After migration, passwords do not work to login into accounts of new computer

Hi 1-5-8,

Thanks for contacting Apple Support Communities!

We understand that after migrating from your previous iMac to your new iMac, you're unable to sign into any user accounts, correct?

If so, you may consider resetting the login passwords as outlined here: Change or reset the password of a macOS user account in macOS Mojave or earlier

"Reset your password

If you don't remember your password, or it isn't working, you might be able to reset it using one of the methods described below. But first try these simpler solutions:

• Make sure that you're typing the correct uppercase or lowercase characters. If your keyboard has Caps Lock turned on, the password field shows a Caps Lock symbol .
• If the password field shows a question mark, click it to display a password hint that might help you to remember.
• Try to log in without a password. If that works, you can then add a password by following the steps to change your password.
• Try to log in with the Apple ID password that you use for iCloud. If you just changed that password and the new password isn't working, try the old password first. If that works, you should be able to use the new password from then on."

We hope this helps you.

Cheers!