How do I put safari back on my iPhone

Safari  icon missing?

Safari is maintained as a part of iOS. There is no self standing version of Safari.

Go step by step and test.

1. Use the App Library to find your apps

     From your Home Screen, swipe left until you see the App Library. 

     Your apps are automatically sorted into categories.

    https://support.apple.com/en-us/HT211345

2. Make sure that Safari is not restricted.

    Settings > Screen Time > Content and Privacy  Restrictions

    Enter Passcode if you have set it up

    Allowed apps > Safari

    Turn it on.

    https://support.apple.com/en-us/HT208982

3. Reset Home Screen

    Settings > General > Reset > Reset Home Screen Layout

    https://support.apple.com/guide/iphone/return-iphone-settings-to-their-defaults-iphea1c2fe48/ios

The Safari app is not one of the apps that can be deleted but with iOS 14 it can be removed from the home screen. If you have iOS 14, 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.