by Ken Task.
Go to the 3.1 server/instance and check the backup defaults area in Site Admin Menu. Make sure that the defaults include the logs/events. Backup the course again. Step through each screen to assure yourself the backup will include everything you can see. Restore the new backup to the 3.7.x instance.
If you still have the old course backup .mbz file, the new backup should be larger than the old.
'SoS', Ken