...Not the same unit but in our unit there's 4 rocker switches as you come in the front door. They are interior lights, porch light, scare light, and step lights. First thing I did was label them with a label maker as they were not identified from the factory.
...I'd turn on all switches, note what's on and turn off 1 at a time and note what turns off. If on switch appears to "do nothing" then pull that switch and check for voltage on both terminals. If no voltage is present on either connection work upstream to find out why.
.....if you identify the switch and it has power but no power at the light then first look at the ground. My step lights are just amber lense clearance lights. Those fixtures with incandescent bulbs are notorious for corrosion. A green discoloration on the bulb socket is typical. I switched all my exterior lights to led and haven't had an issue with corrosion.
2012 Laredo 303 TG
2010 F250 LT Super Cab, long bed, 4X4, 6.4 Turbo Diesel