Is there a washer that keeps the axle from coming loose and if so, what's the part number for it?

Thanks

 

Going from the axel out to the wheel I see 2 snap rings, the wheel hub, then a washer, lock nut, and finally the cotter pin.

Which piece are you looking for?

 

I believe it's either the two snap rings or the washer.

 

My AllData isn't specific on which rings are which. Looks like the 2 on the outside of the axle could be the same. There's also one that's used to rebuild the inner axle itself. Suggest going to a Nissan parts dept to be sure.