My App Store has disappeared from my iPad

The App Store app is not one of the apps that can be deleted but it can be removed from the home screen. Go to the App Library (swipe left past your last home screen). From there you can touch and hold an app and slide it left back to the home screen.

Another reason for it not being visible is due to a restriction on purchasing. Go to Settings and tap Screen Time, tap Content & Privacy Restrictions, tap iTunes & App Store Purchases, choose a setting and set to Allow. See: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support

Assuming that your iPad is not centrally managed by a business or educational establishment, if neither the App Store nor ScreenTime settings are visible, a forced-restart of your iPad may be beneficial. A restart will very often clear an isolated software issue:

Connect your iPad to its Power Adapter and allow the iPad to charge, undisturbed, for at least an hour. While still connected to external power, try a forced-restart:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

If you continue to experience difficulties, you may need to seek assistance directly from from Apple Support. You can contact the Support Team using the Get Support link at top-right of this page. Alternatively, you can initiate and manage your support cases using the excellent Apple Support App. While recognising that you currently have difficulties accessing the App Store, when able, the App can be downloaded from the App Store:

https://apps.apple.com/gb/app/apple-support/id1130498044

What happens when you search? See: Use Search on your iPhone, iPad, or iPod touch - Apple Support