As you may realise, deleting (not Offloading) an App from your iPad will also delete all associated data. Once deleted, your only hope is to restore a pre-existing iCloud or iTunes backup to your iPad. Before restoring data from the backup, you'll first need to reinstall the deleted App.
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Be aware that restoring a backup will overwrite all data on your iPad with that of the backup. You also need to understand that if the existing iCloud backup has been refreshed since deleting the App, any data associated with that App will have been purged from the backup - and will be unrecoverable.
If you don't have a backup of your missing data, that data will have been irretrievably lost.