This site is excellent for finding English-translated Japanese exclusives and "undub" versions of classic RPGs.
Simply downloading the file isn't enough; your PSP needs to recognize the ISO files.
If you are running out of space, use a tool like PSP ISO Compressor to turn ISOs into CSOs. Note that some high-end games (like God of War ) might stutter slightly in CSO format.
Move your .iso or .cso files directly into that ISO folder.
Here is a comprehensive guide on how to find these games and ensure they work perfectly on your handheld. Why Use ISO Format for PSP 3001?