I have an old desktop MAC Pro and I lost the password how do I get in to change it?
How to open a desktop Mac without the password
Question marked as
Do you care about the contents of the old Mac Pro?
No:
… Erase and reinstall macOS - Apple Support
Yes:
… If you forgot your Mac login password (Catalina and newer)
… Change or reset the password of a macOS user account in macOS Mojave or earlier - Apple Support