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 to the Home Screen.
The exception to that is that it can be deleted in the European Union if you had first installed an alternative. For information on reinstalling in the European Union, see: Delete certain built-in apps from your iPhone or iPad in the European Union - Apple Support
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. Also see the following Apple Support article for more information: Use parental controls to manage your child's iPhone or iPad - Apple Support