On your new OpenFire server where you know the admin password, use MySQL to do your SELECT query and see its hashed password (I believe its the encryptedPassword column, been awhile since I had OpenFire set up). Copy that entire hashed password to your clipboard, then flip over to the old OpenFire server's MySQL DB and do an:
UPDATE ofUser SET encryptedPassword='<paste in password hash here>' WHERE username='admin';
This should then allow you to access the old OpenFire server using the password you use on the new OpenFire server. It will only work if the OpenFire server isn't salting hashes using some specific string on a per installation basis.
Alternatively, I found this:
Or, I also found this on the Ignite forums:
Both basically just suggest you tell OpenFire it is an initial installation again, and it'll let you set the admin password (and as long as you pick all the other settings the same it should be fine). I'd definitely take that second person's advice and back up the database first, in case the setup wizard goes and wipes out your database or something.