How to remove the parental lock on an Xbox 360 when you've forgotten the password?
Solution 1:
Your dad can reset the passcode by answering the secret question from when he set up the controls. To do this, enter an incorrect code and one of the options will be to reset the passcode. Answer the secret question and enter a new code.
If your dad has also forgotten the secret question, it gets a little trickier. If the console is registered to an adult's account in their name, log into that and select it from devices. You can reset the code there.
If not, you (that is to say your dad) will need to contact Xbox Support