gvarner wrote:
Delete the folder where you thought you put them. Close File Explorer. Reopen Explorer and create the folder again, being careful to note the path. Then open your SD card, Select All, and Copy. Then Paste into the new folder you just created. If they don't show up, restart your PC and do it again. If that fails, you may have a Windows 10 problem. Windows 10 does have a codec file that is able to view the JPEG that's inside of RAW files.
THAT IS WRONG INFORMATION!!! The problem has nothing to do with how the files were downloaded to the computer. Nikon cameras come with a CDROM that contains a program called "PICTURE CONTROL UTILITY" or "VIEW NX". They are basic editing programs and will open the RAW files that have already been successfully transfered to the computer.