They use 9mm Largo, which is a bit longer than 9mm Luger. IIRC, 9mm Largo is about as long as a .38 super round and about as powerful as 9mm Luger. You may be able to have it rechambered or rebarreled for 9mm Luger to have a more common ammo (not sure on that one).
Judging from the condition it is listed as having (poor bore and needing major work) I'd pass and try to find one in better shape.
From what I have read they are neat little guns though - kind of like a scaled down mauser that fires a pistol round.