Depending on the version you started the upgrade from the username and password may have now changed.

If you upgraded from 2.2.0.5322 , your user name and password have changed. Log in using the new default credentials:
username: admin
password: Admin1


If you upgraded from 3.0.0.x, the username and password have not changed, and you log in with the same credentials that you started with at the beginning of this upgrade.