How is that in any way related to this forum? FWIW: you need admin rights on your Linux system to change passwords. Not related to the Graphical User Interface

How to I recover a forgotten password for Linux Mint? I really like Linux mint but installed it on an older thinkpad computer that I am returning to service and although I can get into the system and use it, I can't access new software and every time I am asked for the password, I am told it is wrong. How do I recover it or change it?

Sounds like you used a different password for the root account, if you don't remember it I am sorry but there is no way of retrieving it. It works the other way round only, Root can reset user passwords.