Hello @PayGro !
Welcome to Microsoft QnA!
Please follow this guide:
https://learn.microsoft.com/en-us/iis/manage/configuring-security/how-to-set-up-ssl-on-iis
Since you are on IIS you dont need App service !
I hope this helps!
Kindly mark the answer as Accepted and Upvote in case it helped!
Regards