How do I transfer password to a new iphone

Do you mean an Apple ID password, the Screen Time passcode or the screen unlock passcode?

For the Apple ID password just go to Settings and tap Sign In at the top, and enter your Apple ID password.

For the screen unlock passcode it does not transfer, but you can enter the same passcode as the old phone during setup.

For the Screen Time passcode if you follow the instructions in the Related Article at the top of this page the Screen Time passcode will transfer to the new phone.