PPSSPP is an open-source emulator that runs PSP games on non-Sony hardware. It requires a digital ROM (ISO or CSO file) of a PSP game. The PSP did receive a Grand Theft Auto: San Andreas port? The PSP received:
Use an app like ZArchiver to extract the .7z or .zip file from Mediafire. Gta San Andreas Definitive Edition Ppsspp Download Mediafire