how do you erase passcode on iphonmax12pro

The passcode - the four or six digit number used to lock an individual device - is stored only on the device, and so cannot be retrieved. I'm afraid you will have to erase it. Please see If you forgot the passcode on your iPhone, or your iPhone is disabled - Apple Support

If you have forgotten your Apple ID please see If you forgot your Apple ID - Apple Support (though if you've erased the phone you should be able to set it up with your current Apple ID instead).

To restore the iPhone, follow the instructions in the Related Article above.

Check your web browser's autofill entries, or use Apple's iForgot service, or contact their Account Security team, or if you're the iPhone's original owner and have encountered the activation lock, click here and submit an unlock request.

(201834)