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.)?
Install a program like WinRAR or 7-Zip . DarkSoulIII.La.Ciudad.Anillada.part1 (3).rar
I can provide the specific steps or troubleshooting for extracting the RAR file. If you are trying to using "par" files