All purchases in Feeld, including Majestic Membership, Pings, and Uplifts, are managed by the App Store on iOS or Google Play on Android. Your receipt will be sent to you directly by your app store.
If you want to retrieve a copy of your receipt from your app store, see these Google and Apple resources on how to do that:
iOS
View your purchase history for the App Store and other Apple media services
Android
Find your Google Store receipt & order number