The files are located in the .jar file in the VERSIONS folder of where your games installed. Easiest way to reach it is to go in game, go to the resource packs options and click the button that opens the pack folder, back out one folder and you'll be in where your games installed. go into VERSIONS, and locate the version folder your profile is linked to. 1.8 etc, in there is a .jar of the same file name. Ipen it in winrar/winzip, and then drag out the ASSETS folder. That holds all the games graphics.
How do i get the default texturepack