Take a look at page 3 of the nostalgiaair.org (this site, under Resources) data for this set. This will tell you all you need to know. There are at least four knobs: Tone, Volume, Tuning, and Band Select.
Looks like Tone is at the far right of the set looking at it face-on. Volume has a power pull-on-push-off feature so you can tell which one that is easily. The Tuning knob is pretty obvious and the Band Selector is the one that has three positions (and which will be probably fairly difficult to turn). Good luck getting this battery set working- you will need a multi-voltage DC supply.