Link app purchase system to stores and launch app in Google Play Store and Apple App Store

We have a web app that we want to compile and publish for Apple and Android. There is a section for buying credits. They reject our publication because in-app purchases are not allowed. To solve this, they told us that purchases should be made within the stores.

1 Transition in-app purchases to purchases through the Store
2 Publish the app for Android and iOS (we will provide the necessary text and screenshots) This has 2 stages, publication in testflight mode and then final publication after tests.