Change backed up volume on client with cmd?

Is there a way to change which volume you want to be backed up with command line?
I have seen the set-settings command, but it does not seem to work right.

This is the command I have been trying to run:
UrBackupClient_cmd.exe set-settings -k image-letters -v D

This is the result:
Error setting settings

Am I missing something? Any insight is appreciated