No plug-in is needed to import RAW files from a Nikon D7100 to LR5.
However, if you have used certain versions of Nikon software to move the photos from the camera to a hard disk, then this may be interfering, and causing LR to not recognize the photos. The solution is to import directly from the camera card to Lightroom (if the photos are still on the camera card), or if not try http://owl.phy.queensu.ca/~phil/exiftool/fix_corrupted_nef.html
This fixed my problem. I wont use Nikon Transfer 2 again. Thanks for the info and the timely response!