I imported some jpg files on an iMac 21 files. They were in Drop box. I used Light Room to import them.. I had it made a copy just in case and it converted both the original and the copy to nac files. Light room converted the files to nar files. The nar file extension means they are Nikon files. I do not have a Nikon camera nor any nikon software. Now I cannot do anything with the files.