How can I reset the password on the iPad

If you know your code, you got to Settings>Passcode & Touch ID>Change Passcode. If you forgot it but still aren’t locked out, you can go Settings>General>Reset>Erase All Content and Settings. If you are locked out, you will need to Reset your iPad.

See Change your Apple ID password https://support.apple.com/en-us/HT201355

And, here is What to do after you change your Apple ID or password https://support.apple.com/en-us/HT204071

Apple ID password? Enter the Apple (iCloud) ID and click Forgot Password.

Apple ID - Manage            

Apple ID – Forgot Password