Reinstall the App Store app.
How do I reinstall and download the App Store app on this phone apple 8s
iPhone 8 Plus, iOS 13
Question marked as
The App Store app isn't one of the built-in apps that can be deleted. The usual reason for it not being visible is due to a restriction on purchasing. See: Use parental controls on your child's iPhone, iPad, and iPod touch - Apple Support
If that isn't it the other step is to use Search to try to locate it. Use Search on your iPhone, iPad, or iPod touch - Apple Support