App Store app disappear in ipad

The Apple App Store App is an integral element of iOS/iPadOS - and cannot be deleted. The App can however be moved to an App folder - or removed from your Home Screens altogether. If any Apps are removed from the Home Screen, they will always be accessible from the App Library.

Information about organising your Apps and using the App Library can be found here:

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

To reiterate, the App Store App cannot be deleted from iPad - as without it, you cannot install any Apps from the App Store.

Perhaps your iPad is centrally managed by a School, Educational establishment or business? If so, applied policy restrictions may prevent access to the App Store.

Not if your device is managed. I wish I could get to it...