i was wondering how whoever converted rhen var citadel in the bf1 conversion pack made it so the units did not appear black when inside the tomb area.

hmm, sounds like a lighting issue...

yes when i converted it, i did remember to add lighting so the objects themselves appear lighted, but what type of lights do i need inside the tomb so units can be lit up inside and how should they be placed. Directional lights don't seem to do the trick.

I looked at Rhen Var: Citadel (which was lit by Rends) to figure out how he did it. What he did was create regions that covered the 'indoors' parts. Then he set the region type to shadow. Once that's set you can change the lighting settings for each shadow region on the right-hand side of that region's properties.