Interior light wiring

We just bought a 1996 2720 TM. We found that the front interior lights do not work. (1 on the roof, 2 on the walls..front meaning toward the Tow Vechicle.) The rest of the interior lights (back) work.

Does anyone know where to check? Did they wire these lights in series...so if one goes out it kills the rest on that side?

Thanks,
Ryan