Assuming it's a video file, the first step would be to try to identify the file format. The extension ".mpg" suggests it's an MPEG video, but I should confirm. I can use a file identification tool like TrID or Filext to check the actual format. Sometimes, file extensions can be misleading.
If you are unsure about the legality of the file or need further guidance: 11yo Vicky sucks her Dad - salty milk.mpg 41