Trouble centering header

Question

I just want to center these 4 anchor tag lis inside of this ul.

Is there someway I can wrap these four into one container, and then move them to the left with CSS? I just want those 4 items to appear centered in that ul.

Here's a picture of what I'm talking about

Below is my total header in HTML. There's a lot of CSS so I don't know what to link people to but I'll put what i have been playing with below.

    <!-- Header -->
        <header class="header header-fixed header-fixed-on-mobile header-transparent" data-bkg-threshold="100">
            <div class="header-inner">
                <div class="row nav-bar">
                    <div class="column width-12 nav-bar-inner">
                        <div class="logo">
                            <div>


                                <a href="tel:1-530-680-8255"  style="color:grey; display:inline-block">1-530-680- 
                                        8255</a>

                                         <a href="tel:1-530-680-8255"><i class="fas fa-phone" style="display:inline-block"> 
                                          </i>1-530-680-8255</a>



                            </div>
                        </div>
                        <nav class="navigation nav-block secondary-navigation nav-right">
                            <ul>



                                    <li class="aux-navigation hide">
                                        <!-- Aux Navigation -->
                                        <a href="#" class="navigation-show side-nav-show nav-icon">
                                            <span class="icon-menu"></span>
                                        </a>
                                    </li>
                                </ul>
                            </nav>
                        <nav class="navigation nav-block primary-navigation nav-center">
                            <ul>

                                <li class="current"><a href="index.html">Home <i class="fas fa-home"></i></a></li>
                                <li class="current"><a href="index.html">About <i class="fas fa-at"></i></a></li>
                                <li class="current"><a href="index.html">Services <i class="fas fa-wrench"></i> </a></li>
                                <li class="current"><a href="index.html">Contact <i class="fas fa-phone"></i> </a></li>


                                            </ul>
                                        </li>
                                    </ul>
                                </li>
                            </ul>
                        </nav>
                    </div>
                </div>
            </div>
        </header>
        <!-- Header End -->
---CSS---

nav ul li  {
display: inline-block;
text-align: center;
width: 100px;
margin: 00px;
padding: 0px;
 }

Answer 1

Sarah, or others:

The solutions provided have centered it, however the phone number is now cutoff.

cutoff phone number

Im including all of what i think is the relevant CSS. I hope this isnt too much to sift through, i just have no clue what is causing this.

    [4. Header Styling]
*/

/* Initial Position */
.header-bottom{
    bottom: 0.1rem;
}

/* Intial Height */
.header .logo,
.header .header-inner .navigation > ul > li,
.header .header-inner .navigation > ul > li > a:not(.button),
.header .header-inner .dropdown > .nav-icon{
    height: 8rem;
    line-height: 8rem;
}

/* Compacted Height */
.header-compact .logo,
.header-compact .header-inner .navigation > ul > li,
.header-compact .header-inner .navigation > ul > li > a:not(.button),
.header-compact .header-inner .dropdown > .nav-icon{
    height: 6rem;
    line-height: 6rem;
}

/* Header Initial Styling */
.header .header-inner{
    background-color: #fff;
    border-bottom: none;
    border-bottom: 1px solid #eee;
}
.header .header-inner > .nav-bar{
    /*border-bottom: 1px solid #eee;*/
}

/* Transparent Header Initial & Active Nav Colors */
.header-transparent .header-inner{
    background-color: transparent;
    border-bottom: 1px solid transparent;
}
.header-transparent .header-inner > .nav-bar{
    border-bottom: 1px solid rgba(255,255,255, 0.2);
}

/* Background Header - On Scroll! */
.header-background .header-inner{
    background-color: #fff;
    border-color: #eee;
}
.header-background .header-inner > .nav-bar{
    border-bottom: none;
}

/* Header Inner Top */
.header .header-inner-top{
    height: 4rem;
    background: #232323;
    color: #fff;
}

/* Mobile Header Styles & Breakpoints */
.mobile .header .header-inner{
    background-color: #fff;
    border-top: none;
}
.mobile .header .header-inner{
    border-bottom: 1px solid #eee;
}
.mobile .header + .content{
    padding-top: 0;
}
@media only screen and (max-width: 960px){
    .header .header,
    .header .header-inner,
    .header.header-transparent .header-inner{
        background-color: #fff;
    }
    .header .header-inner{
        border-bottom: 1px solid #eee;
    }
    .header .header-inner > .nav-bar{
        padding: 0;
    }
}

/*------------------------------------------------------------------
[5. Header Logo]
*/

/* Initial Logo Width */
.header .logo{
    width: 12.5rem;
    top: 30px;
    left: 0px;
    position: absolute;
}

/* Compacted Header Logo Width */
.header-compact .logo{
    width: 12.5rem;

}

/* Initial Logo Styling */
.header .logo a{
    display: block !important;
    position: absolute;
    top: 0;
}
.header-in .logo a,
.header-out .logo a{
    -webkit-transition-duration: 0ms;
    transition-duration: 0ms;
}
.header .logo a:first-child{
    opacity: 1;
    -webkit-transform: translateY(0);
    transform: translateY(0);
}
.header .logo a + a{
    display: none !important;
}

/* Transparent Header Show Light Logo */
.header-transparent .logo a:first-child{
    opacity: 0;
    -webkit-transform: translateY(5rem);
    transform: translateY(5rem)
}
.header-transparent .logo a + a{
    display: block !important;
    -webkit-transform: translateY(0);
    transform: translateY(0);
}

/* Header Background Logo Swap to Dark Logo - On Scroll! */
.header-background .logo a:first-child{
    opacity: 1;
    -webkit-transform: translateY(0);
    transform: translateY(0);
}
.header-background .logo a + a{
    display: block !important;
    opacity: 0;
    -webkit-transform: translateY(-5rem);
    transform: translateY(-5rem);
}

/* Logo Nav Dark */
.nav-dark .logo a:first-child{
    display: block !important;
    top: 0;
    opacity: 1;
    -webkit-transform: translateY(0);
    transform: translateY(0);
}
.nav-dark .logo a:last-child{
    display: none !important;
}

/* Logo Mobile Header & Breakpoints */
.mobile .header .logo a:first-child{
    display: block !important;
    opacity: 1;
    -webkit-transform: translateY(0);
    transform: translateY(0);
}
@media only screen and (max-width: 960px){
    .header .logo-inner{
        display: table-cell;
        vertical-align: middle;
    }
    .header .logo a{
        position: relative;
    }
    .header .logo a:first-child{
        opacity: 1;
        top: 0;
        -webkit-transform: translateX(0) !important;
        transform: translateX(0) !important;
    }
    .header .logo a:last-child{
        display: none !important;
    }
}

/*------------------------------------------------------------------
[6. Header Navigation]
*/


/* Padding & Margins */

<style>
  .navigation {
    width: 100%;
    display: block;
    clear: both;
  }

  .navigation ul {
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    width: 100%;
  }

  .navigation ul li {
    text-align: center;
    width: 100px;
    margin: 0;
    padding: 0;
    display: block;
  }
</style>


.header .logo-center ~ .navigation.nav-center{
    padding-top: 0.5rem;
}
.header .logo-center ~ .navigation.nav-center > ul > li > a{
    padding-bottom: 2rem;
}
.header .navigation > ul > li > a{
    margin: 0 1.5rem;
    padding-left: 0;
    padding-right: 0;
    font-size: 1.1rem;
    text-transform: uppercase;
    font-weight: 500;
    letter-spacing: 0;
}

/* Header Initial & Active Nav Colors */
.header .navigation > ul > li > a{
    color: #999;
    opacity: 1;
}
.header .navigation > ul > li.current > a,
.header .navigation > ul > li > a:hover{
    color: #000;
    opacity: 1;
}
.header .navigation > ul > li.current > a:hover{
    color: #000;
}

/* Transparent Header Initial, Hover & Current Nav Colors */
.header-transparent .navigation > ul > li > a{
    color: #fff;
    opacity: 0.6;
}
.header-transparent .navigation > ul > li > a:hover{
    color: #fff;
    opacity: 1;
}
.header-transparent .navigation > ul > li.current > a,
.header-transparent .navigation > ul > li.current > a:hover{
    color: #fff;
    opacity: 1;
}

/* Nav Dark Initial, Hover & Current Colors */
.header-transparent.nav-dark .navigation > ul > li > a{
    color: #000;
    opacity: 0.5;
}
.nav-dark .navigation > ul > li.current > a,
.nav-dark .navigation > ul > li.current > a:hover{
    color: #000;
    opacity: 1;
}

/* Header Background Initial, Hover & Current Nav Colors - On Scroll! */
.header-background .navigation > ul > li > a{
    color: #999;
}
.header-background .navigation > ul > li.current > a{
    color: #000;
    border-bottom: none;
}
.header-background .navigation > ul > li.current > a:hover{
    color: #000;
}
.header-background .navigation > ul > li > a:hover{
    color: #000;
    opacity: 1;
}

/* Sub Menus, Mega Menus, Dropdown List Initial Colors */
.navigation .sub-menu li,
.navigation .dropdown-list li{
    border-bottom: none;
}
.navigation .sub-menu li a,
.navigation .mega-sub-menu ul li a,
.navigation .dropdown-list li a{
    line-height: 1.6;
    font-weight: 400;
    font-size: 1.2rem;
    color: #888;
}
.navigation .sub-menu:not(.custom-content) li a,
.navigation .dropdown-list:not(.custom-content) li a{
    padding: 1rem 1.5rem;
}
.navigation .mega-sub-menu > li > a{
    font-size: 1.3rem;
}
.navigation .sub-menu:not(.custom-content) a,
.navigation .sub-menu.custom-content,
.navigation .mega-sub-menu,
.navigation .dropdown-list{
    background-color: #111;
}

/* Menu Nav Cart Intial Colors */
.navigation .cart .badge{
    top: -0.4rem;
    left: 1.2rem;
    background-color: #9a9484;
}
.navigation .cart-overview .product-title{
    color: #fff;
}
.navigation .cart-overview .product-price,
.navigation .cart-overview .product-quantity{
    color: #999;
}
.navigation .cart-overview a.product-remove{
    background-color: #444;
    color: #999;
}
.navigation .cart-overview .cart-subtotal{
    color: #fff;
}
.navigation .cart-overview .cart-actions{
    border-color: #444;
}
.navigation .cart-overview .checkout.button{
    background-color: #9a9484;
    border-color: transparent;
    color: #fff;
}
.navigation .cart-overview .checkout.button:hover{
    background-color: #666;
    border-color: transparent;
    color: #fff;
}

/* Sub Menus, Mega Menus, Dropdown List Hover Colors */
.navigation .sub-menu:not(.custom-content) li:hover > a,
.navigation .mega-sub-menu:not(.custom-content) ul li:hover > a,
.navigation .dropdown-list:not(.custom-content) li:hover a{
    background-color: #000;
}
.navigation .sub-menu li > a:not(.button):hover,
.navigation .mega-sub-menu ul li > a:not(.button):hover,
.navigation .dropdown-list li > a:not(.button):hover,
.navigation .cart-overview .product-title:hover,
.navigation .cart-overview .product-remove:hover{
    color: #fff;
}
.navigation .sub-menu li.current > a:not(.button),
.navigation .dropdown-list li.current > a:not(.button),
.navigation .mega-sub-menu ul li.current > a:not(.button){
    color: #fff;
}

/* Mega Menu Position */
.navigation .mega-sub-menu{
    left: 0;
    right: 0;
}

/* Labels Sub Menu */
.sub-menu li .label,
.mega-menu li .label,
.dropdown li .label{
    margin-left: 0.5rem;
    padding: 0.1rem 0.4rem;
    font-size: 1rem;
    text-transform: uppercase;
    background-color: #9a9484;
    border-color: #9a9484;
    color: #fff;
}

Answer 2

I would do it by adding this css (instead of the one you've displayed):

<style>

  .logo {
    max-width: 300px;
    width: 30%;
    float; left;
    display: block;
  }

  .navigation {
    display: block;
    clear: both;
    max-width: 70%;
    float: right;
    width: 700px;
  }

  .navigation ul {
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
  }

  .navigation ul li {
    text-align: center;
    width: 100px;
    margin: 0;
    padding: 0;
    display: block;
  }
</style>

So you can just add all that code in the <head>-section of your site, and then it should work.