Re: BB 8830 to 9320 Switch: Desktop Manager v6 or v7?
As I say, whatever version of DM you have installed, try it with the OS 7 device. My guess is that if the backup works on that device then a restore should work on that device. If you want to reduce risk, then go ahead and load the latest DM on one of your computers and use that (or use that as well, running backups on two different systems).
However, a caveat. If it matters (if it's important) then have a plan in the event you need to restore and restore doesn't work.