The thing is that the App Store app cannot be deleted from the iPhone. It should still be there on the iPhone. You stated that you have searched the App Library and couldn’t find it. I recommend that you attempt to find the App Store app again by invoking the search option from the Home Screen. Tap on Search located at the bottom of every Home Screen page and search for the App Store. If you find it, then drag it to the location of your choice.
If, for any reason, the above does not work, then you can reset the Home Screen layout and check whether that restores the app on the Home Screen. To do this, open Settings ➡️ General ➡️ Transfer or Reset iPhone ➡️ Reset ➡️ Reset Home Screen Layout.
Axel F.