Welcome to Microsoft Q&A Platform. Thank you for reaching out & hope you are doing well.
I understand that you are trying to select an existing Azure Front Door Premium profile when creating an Azure WordPress web app, but the list doesn't show the profile you would like to select.
As @Silvia Wibowo asked above, could you please confirm if you are trying to create the WordPress web app in the same subscription as the Azure Front Door Premium?
I tried creating an Azure WordPress web app in my lab and I was able to select the Premium SKU Azure Front Door from the list. You can see the below screenshot:
So, I would request you to validate the subscription where you are trying to create the WordPress App and make sure that the Azure Front Door Premium also belongs to the same subscription.
Kindly let us know if the above helps or you need further assistance on this issue.
Please "Accept the answer" if the information helped you. This will help us and others in the community as well.