The last FIFA game officially released on PSP was FIFA 14 (North America) / FIFA 15 (Europe only, as a legacy edition). After that, EA stopped supporting the PSP entirely.
The author of this article does not condone piracy. You should only download FIFA 16 PSP ISOs if you own the original UMD disc. Creating your own backup from your personal disc is the only 100% legal method in most jurisdictions. fifa 16 psp install