There is no official full-version download for on PC. Unlike other main titles in the franchise, Call of Duty 3 was developed by Treyarch as a console-exclusive and was never released for the PC platform. Why Call of Duty 3 is Not on PC
: It remains the only major numerical installment in the series not to receive a PC port. Call of Duty 3 Game Download For PC Full Version
: Tools like RPCS3 (a PlayStation 3 emulator) can run the game at high resolutions, such as 4K. There is no official full-version download for on PC
If you are looking for more recent titles with the number "3" that are available on PC, you can find them through official launchers: : Tools like RPCS3 (a PlayStation 3 emulator)
If you're interested in how the console version looks when running on a PC via an emulator, you can see it in action here:
: Available for purchase on Battle.net and Steam . Black Ops III : Also available via the Steam Store .