Thats what I had in mind, but as Visvanath as well mentioned, how come you can upgrade an older database while newest should be on moodle.
anyway, what you can do is, fire up another instance of moodle on your previous version, let it install (alone with all plug-ins to be on safe side) and then replace the database with db2.sql, it should work fine, now take course backups and import those into newer moodle.
This is by far only was possible, if the courses were many, if not, then simply recreate the courses