TWO SCENARIOS:
If YOU are talking about the MySQL password for the DATABASE then:
He probably means that you need to pick a new password, and enter that in your MySQL screen, whatever that is ... as well as put it into your two configure.php files.
ie: tell your database what new password you want to use, and then tell Zen Cart what that new password is.
The password in the Zen Cart configure.php files is not hashed. There's no need to unhash it.

If YOU are talking about the password field in the "admin" table inside your database, then:
- as RodG says, this password is hashed, and you cannot retrieve that value from the database
- But then you'd have no reason to "be certain you know the password" because you'd clearly already be using that password when you login to your store's admin section.
- If indeed you ARE talking about that password, then you can reset it by using the "Forgot Password" link on the login screen
- If you are unable to use that for some reason, you can do a forced reset using these instructions: https://www.zen-cart.com/tutorials/index.php?article=2
But none of this should be necessary whatsoever, given that you already had the admin login password as evidenced by your own ability to login to your store's admin area ... which is why I made the assumption that your confused jargon was referring to the database as a whole, in my first reply.