Why is’nt App Store not available in my device

iPad, iPadOS 15

Use App Library to search the App Store app, see Use the App Library and Home Screen to organize your iPad apps

Use the App Library and Home Screen to organize your iPad apps - Apple Support

• If you have find the app, tap & hold on the app, then drag to the Home screen & drop it.

You have quick access to App Library by tapping the App Library icon in the iPad's Dock.