Because these are unofficial, you won't find them on the PSN store. Instead, users typically source them from community repositories:
Running on a PlayStation 3 is primarily done through homebrew emulation, as there is no official native port like there is for Super Mario 64 . While Super Mario 64 was natively ported thanks to a source code leak, Mario Kart 64 generally requires a Nintendo 64 emulator (like retroArch ) to run on a jailbroken PS3. Feature Expectations for MK64 on PS3 mario kart 64 pkg ps3
(best compatibility) → converted to PKG Because these are unofficial, you won't find them
Mario Kart 64, a classic Nintendo 64 racing game, is a highly sought-after title for its multiplayer fun and iconic tracks. Although originally released for the Nintendo 64, enthusiasts often look for ways to experience this game on modern consoles, including the PlayStation 3 (PS3), through various packaging (PKG) files. Feature Expectations for MK64 on PS3 (best compatibility)
Some homebrew creators bundle the ROM and an emulator into a single "forwarder" PKG. You can find various versions and fan-made collections on the Internet Archive .