If Java's idea doesn't work... which it might not if the bulbs are old... you may have to dismantle the ballast pack and look at what the ballasts are rated for.
ok, there are 2 ballasts they have stickers on them that read:
1) 175w 120v 3.7 amps
2) 110w 120v 2.1 amps
i'll assume that the 175w are the metal halides and the 110w are the vho's