How can I reinstall Safari on my iPhone?

Safari 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