If you tell me whether you’re on or PPSSPP , I can give more specific steps to compress your own legal copy.

: The PSP port was praised for maintaining the solid gameplay of the PS2 original, though some found the camera controls slightly clunkier on the portable device. Game Review: The Warriors (PSP) - Ars Technica

The Warriors is copyrighted by Rockstar Games and Take-Two Interactive. Downloading a compressed ISO is technically piracy unless you own an original UMD or digital license. However, many retro gamers consider downloading a backup copy of a game no longer sold commercially as a grey area. Proceed with awareness.