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 Password
Change or reset the password of a macOS user account:
https://support.apple.com/en-us/HT202860
From recovery mode:
At one time you could change password from recovery mode.
https://www.hongkiat.com/blog/reset-osx-user-account-password/
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.
http://support.apple.com/kb/HT1492
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/fsck -fy
/sbin/mount -uw /
cd /var/db
pwd
#List all files. The l is a lower case L.
ls -a
#The move command acts as a rename command in this format.
mv -i .applesetupdone .applesetupdone.old
# reboot your mac
shutdown -r now
what's a firmware password??
