Accidentally deleted App Store

App Store cannot be deleted.

Check in the app library in the last page of screens, and drag it back to where you want it.

Alternatively, if Screen Time has been enabled, here’s how to enable or disable access to App Store: Use parental controls on your child's iPhone and iPad - Apple Support

Use the App Library to search for the App Store by swiping all the way to the left and searching App Store, then drag the App Store back onto your Home Screen.

Make sure you don’t have Screen Time Restrictions enabled, go to Settings > Screen Time > Content & Privacy Restrictions > iTunes & App Store Purchases > Installing App, and set it to Allow.