i can't change my phone passcode there is no option for it

If the option is not in Settings, then you have Screen Time restrictions turned on preventing access.

Go to Settings > Screen Time > Content & Privacy Restrictions > Passcode Changes, and change it to Allow.

Settings > [Face/Touch] ID & Passcode > Change Passcode

Well, to change the passcode, you must first be able to get into the phone's settings using the current passcode.

Are you able to do this? Or, did you forget the passcode or enter it incorrectly too many times?

Does the phone say "Unavailable" or "Security Locked"?