You only need your Backup-Tapes, not the old server...
Anyway, you could go the other way round now:
- install a fresh Moodle 2.x from scratch
- make as much Backup-Zip-Files as you can on your running server
- copy and restore them into the new Moodle 2.x instance
Unfortunately the question will persist, what the data of your missing activity module will become on a Moodle without that module. I have no idea how data consistency is treated in such cases. I fear this is the price we have to pay for all the nice modularity we have in Moodle. But we learned a lesson here: uninstall your 3rd party modules/plugins before upgrading to Moodle versions not offering those modules/plugins. And if you need those modules/plugins, DO NOT upgrade. Freeze everything and start over with a new server like I did. A major upgrade is always the good moment to start over from scratch.
Rosario