You will likely get a .7z , .rar , or .zip archive. A 180 MB download will extract to roughly 250 MB (if it’s CSO) or back to 800 MB+ (if it’s ISO with dummy data restored—rare).
Search for "Midnight Club 3 DUB Edition CSO" or "Midnight Club LA Remix CSO". The .CSO file format is a compressed ISO, which is what you're looking for. midnight club psp highly compressed