The Unknown Pokemon (Unown) were first introduced in Pokemon Gold and Silver, and they are only available in those games and their remakes, HeartGold and SoulSilver.
If you are looking for a specific Pokemon, you can try the following:
* Check the Pokedex: Each Pokemon has a specific location where it can be found. You can check the Pokedex for its location and then go to that area.
* Use the PokéRadar: This item can help you find specific Pokémon in certain areas. The PokéRadar can be found in the Goldenrod Department Store.
* Trade with other players: Trading is a great way to get Pokemon you haven't found yet. You can trade with other players online or in person.
* Breed Pokemon: You can breed Pokemon to get new eggs with different Pokemon. You can also use the Day Care to hatch eggs.
Remember, catching Pokemon can take time and effort, so be patient and persistent!