How do I erase this whole phone with out a computer and I don’t know the password because I found the phone

IF the iPhone has iOS version 15.7.1 installed on it then you can reset the passcode and erase the iPhone. You will still need the original owner's Apple ID and Password to finish the reset. Plus, the iPhone will have an Activation Lock on it and it can only be removed with the original owner's Apple ID and Password.

My recommendation is that you had that iPhone over to the local authorities so that the original owner can find it if s/he wants to. Thanks.

Axel F.

You will probably encounter Activation Lock which requires the Apple ID and Password of the original owner of the device. This is an anti theft feature which cannot be by-passed. You should make some attempts to return the phone to the owner as it will remain useless for you. Turn in to Lost and Found, the Police or you can recycle it at any Apple Store.