Unofficial "repacks" are a common vector for trojans, miners, and ransomware. Since these files are not verified by Activision or Steam, there is no guarantee of safety.
You only need to right-click the first file (Part 1) and select "Extract Here" using software like WinRAR or 7-Zip . The software will automatically pull data from Part 2 and the remaining segments. Risks of "Areal Gamer" Repacks download-call-duty-black-ops-areal-gamer-part2-rar
You cannot extract the game with just part 2. You need part 1, part 3, and so on, all located in the same folder. Unofficial "repacks" are a common vector for trojans,