How do I reinstall my Safari app on my iPhone?

Are you sure it's gone? It seems strange that Safari has been deleted.

Check in Settings -> Screen Time -> Content & Privacy Restrictions -> Allowed Apps if Safari has been disabled.

Alternatively check if you have installed a Profiles & Device Management in Settings -> General

You don't. Safari is part of iOS and cannot be removed. It can only be hidden using screen time or a management profile.

You browse the safari in your app Apple store and you reinstall it.