is this the plug?

2000 x5 4.4.

I want to check the fluid level in the rear differential. I only see one square plug. Is this the fill in and drain plug?

Also which fluid do i use? Also is the front transfer case have the same fluid?

There should be two plugs on the differential. There is a plug on the pass. side of the diff. The plug at the lowest point is to drain. The fill plug should be "mid diff" for checking.