Hidden duplicate files on WD Elements external hard drive

Hi.

To save space I recently copied all of my ripped movies (DVD's) from my iMac to an WD Elements external hard drive. I then connected the hard drive to my Samsung TV. As all of my files were ripped to .m4v format my TV wouldn't recognise them. A simple fix was to use NameChanger to simply change the file extension of all my movies to .mp4. My TV recognises and plays the files fine BUT I now have some redundant duplicate files which start with ._ before the name, for example: (._GOODFELLAS.mp4). This is annoying as these duplicate files then appear at the top of my list of movies and do not play on my TV. When I connect the hard drive back to my iMac to try and delete these files, they do not appear to be on my hard drive at all.

Any ideas on how to find and delete these pointless duplicate files from my hard drive? I have already tried to show hidden files on my iMac but they still do not appear.

Thanks in advance.