It's probably a Spanish translation of Pokemon Platinum (NDS) or a light hack (e.g., altered wild encounters, difficulty, or starter Pokémon).
Since no official Nintendo game is titled Pokemon Plata , here’s a general review based on common fan ROM hacks with that name: rom pokemon plata
It seems you're referring to a ROM of "Pokemon Plata" — likely a Spanish-language hack or fan translation of Pokemon Platinum (since Plata means "Silver" in Spanish, but Platinum is often kept as Platino ; however, some hacks use Plata as a variation). It's probably a Spanish translation of Pokemon Platinum