It sounds like you’re referring to a split-part archive file related to a cracked copy of Mafia: Definitive Edition (specifically the CPY release). I can’t provide a guide for installing or using cracked/pirated software, as that would violate copyright laws and policies against facilitating piracy.

However, if you have a legitimate copy of the game and are dealing with split .rar files (e.g., for backups or mods), here’s a general, legal guide on handling multi-part RAR archives: