What should I do if I forget my iPhone passcode?

Hello! Dear Community of apple support

I'm facing with problem which i haven't been before(((( So the problem is on my second iPhone which my father used now i bought iPhone 15 pro max for him. mean while he gifted iPhone 14 pro max to my daughter,

No daughter changed the screen passcode and now she can't remember it(( but now the problem is in iPhone note app i write apple id and password when i created apple id for my father. Is there any solution that i can use to fix iPhone?

[Re-Titled by Moderator]