Where do you find groudon in pearl?

In Pokémon Pearl, Groudon is not available for capture within the game itself, as it is exclusive to Pokémon Ruby. However, you can obtain Groudon by trading from Pokémon Ruby or from events or special distributions that may have occurred in the past. To catch Groudon, you would typically need to go to the Cave of Origin in Hoenn in Pokémon Ruby.