As it can't be deleted, it can't be re-downloaded (which is good because how would you?). So, it's got to be there somewhere. We just need to figure out where.
Have you checked Settings>Screen Time to make sure that you didn't accidentally restrict something? Look specifically at Settings>Screen Time> Content & Privacy Restrictions> iTunes and App Store Purchases. If you have everything under Store Purchases an Redownloads set to "Don't Allow", the App Store will vanish. If you have the App Store disabled here, the next two suggestions won't do any good.
Did you look in the App Library (it's on the screen past the last home page). Type "App Store" into the search box. If you find it, press and hold on the icon and select "Add to Home Screen".
Finally, you can go to Settings>General>Transfer or Reset iPad>Reset>Reset Home Screen Layout. This will put everything pre-installed back to where it was when you first activated the iPad. It will put everything else into alphabetical order. It will also remove any folders you have created.