Have you found the answer to the question?
I'm also looking for the API to create IAP,
pengym
Users receive reputation points by contributing quality content to the forums.
Posts include post and replies published on the forums.
Post authors can mark replies as Accepted to indicate successful solutions.
Apple Developer Forums admins can mark replies as Apple Recommended to indicate an approved solution
Post
Replies
Boosts
Views
Activity
https://developer.apple.com/documentation/appstoreconnectapi/read_in-app_purchase_information