How to sign my app package for the Microsoft Store

Question

Hello I created a small python program that I would like to post on the Microsoft store after having converted it to .exe and then to .msix impossible to open it because it is not signed, I took a certificate at aws private ca but I don't have the private key to convert it to pfx on the microsoft site there is a list of valid operators: https://ccadb.my.salesforce-sites.com/microsoft/IncludedCACertificateReportForMSFT

but there are only public certificates (so in theory it should not be valid). crt impossible to convert them to .pfx I am lost I need help please

Unable to verify the publisher certificate for this application package. Contact your system administrator or application developer to obtain a new application package with verified certificates. The root certificate and all immediate certificates of the signature in the application package must be verified (0x800B010A)