Over the last decade, there have been attempts by the modding community to translate the game. The status of these projects is as follows:
You are searching for the PSP version specifically, likely for portability. Here is why the patched PSP version is now viable: warriors orochi 3 psp english patch upd
Downside: The PSP version lacks the "Xtreme Legends" content (more characters like Sophitia, Achilles, and Joan of Arc). For that, you need the PS3/PC version. Over the last decade, there have been attempts
Because Koei Tecmo did not localize the PSP version, the only available text and audio are in Japanese. Downside: The PSP version lacks the "Xtreme Legends"