How do I unhide an app on my iPad?

The iPad User Guide is a rich and often overlooked source of information about your iPad and iPadOS. Here is a direct link to the section of the Guide that describes how to hide, lock and unhide Apps that are installed on your iPad:

Lock or hide an app on iPad - Apple Support

If instead you refer to Apps in your App Store purchase list, this Apple Support page provides the information that you'll be looking for:

Hide and unhide apps in your App Store purchase list - Apple Support