There is no official Monster Hunter 3 Ultimate for PSP . Searches for a “MH3U PSP ISO” stem from a mix of fan translation patches (for Portable 3rd) and mistaken identity.
Because the base game is Portable 3rd , fans have created mods to inject 3 Ultimate content into the PSP ISO. These are advanced, but they exist: monster hunter 3 ultimate iso psp
The primary reason the "Monster Hunter 3 Ultimate ISO PSP" search persists is the incredible work of the translation group . They released a comprehensive English patch for MHP3rd . There is no official Monster Hunter 3 Ultimate for PSP