How do I reinstall Safari on my iPhone

Safari is installed with iOS updates. You cannot delete Safari and reinstall it.

The Safari 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. Go to Settings and tap Screen Time, tap Content & Privacy Restrictions, tap Allowed Apps. See: https://support.apple.com/en-us/HT201304

As Safari is a part of the operating system, I don't think you can delete Safari. It must be hiding on another page or in a folder you have created.