What do you see on the screen?
I heard of the request for password in other posts after a macos upgrade. I do not think it is a firmware password. I think it is a normal login password.
For login password, try this:
Change or reset the password of a macOS user account:
From recovery mode:
At one time you could change password from recovery mode.
Get the Mac to set up an additional administrative account. You can then change the password on your old account. This will work all all releases of Mac OS X so far.
You need to get into single use mode for steps one and two that are listed below. Start with your computer power off. Hold down command-s. Power on your computer. Continue holding down command-s until you see some text on the screen.
This page will tell you how to get into single user mode.
Type in the following:
The first two commands will depend on your release of Mac OS X. Look at what is typed out in the console to determine the exact format.
# Type the follow two instructions to access the startup disk in read/write. Press return after each command.
# in case of partial success repeat this command until errors go away.
/sbin/mount -uw /
#List all files. The l is a lower case L.
#The move command acts as a rename command in this format.
mv -i .applesetupdone .applesetupdone.old
# reboot your mac
shutdown -r now