Open the archive with WinRAR or 7-Zip . Sometimes the password or the source website is written in the "Comments" pane on the right side of the window.
Be extremely cautious of websites that ask you to complete a "survey" or download a separate "Password Tool" to unlock the file. These are almost always scams or malware. If the source site is not clear, it is safer to delete the file and download the game from a reputable digital storefront . game-airborne.kingdom-(60256).part2.rar
Check the folder where you downloaded the .rar file. Uploaders sometimes include a small text file named "Password.txt" or "ReadMe.txt" in the same directory. Open the archive with WinRAR or 7-Zip