Have my deceased friends iPhone

Sadly my friend passed away from cancer. His iPhone was one of the things among all of his personal belongings he left to me. I believe it’s a iPhone 12 or 12 Pro. I do not have the screen passcode nor do I know his user name or password. Never thought about it because he and I didn’t expect he’d be passing away so suddenly. I do have his death certificate if need be. Can anyone help, please?