Install a program like WinRAR or 7-Zip .
If you are trying to using "par" files (parity files) to create a "paper" (recovery file), you would need to use a tool like QuickPar to repair the missing parts using the .par2 files [1]. If you can tell me: Are you trying to extract the game files? Do you have all the parts (.part1, .part2, etc.)?
Because this is a (a large file broken into smaller, numbered parts like .part1 , .part2 , etc.), you cannot use it alone. Here is what you need to do: