If you are after implementing custom domain for PowerApps Portal for your organization managed by GoDaddy then here is the solution.
Straight to the point:
There is a good official doc by Microsoft about how to add your custom domain for the PowerApps portal
Official URL: https://docs.microsoft.com/en-us/powerapps/maker/portals/admin/add-custom-domain
But if the organization is managing your DNS, CNAME records and domain using GoDaddy as the domain provider, then you may find it difficult to match Microsoft SSL certificate Standard, as GoDaddy does not support the PFX file format. They usually provide SSL certificate in PEM format.
There are many tools like OpenSSL, SSLShopper.com but none of them are working as expected.
Below are the steps to convert your. PEM to .PFX format.
Once you have obtained your custom domain and purchased SSL certificate from GoDaddy
Step 1: Rename the .PEM to .CER format. Example below
Cftsevbnm43cb1055.pem to Cftsevbnm43cb1055.cer
Step 2: Open command prompt with elevated privilege in your local machine and run the following command
E:> certutil -MergePFX Cftsevbnm43cb1055.cer .cer YourPortalCertificate.pfx
In this way, you no need to spend more time using different ways to convert into .pfx. Once you have your .PFX format then follow the official docs to complete the steps to use your new custom domain.