Open Minecraft. Create a few worlds, then go to home screen. Uninstall the game. Then check iCloud backups and see Minecraft Is present in iCloud backup.  Reinstall the game there is no worlds.   Create a few worlds. Go back to home screen.  Do a iCloud back up.  Check to see if Minecraft is present in backup.  When completed backing up do factory reset iPad using erase all content and settings. Then set up iPad and restore from iCloud back up using same iCloud login.  Wait for restore to complete.  Open Minecraft. No worlds.    This happened to me 3 times now.