It is for completing 100 pokedex in Unova. I already have a pansear.
In Pokémon Black and White, a Trainer in the Dreamyard will give the player the monkey with the type disadvantage against the player's starter Pokémon, which will have a type advantage itself against the monkey used by the Gym Leader of the nearby Striaton Gym. Pansage can be obtained in Pokémon Black and White as a gift Pokémon at the Dreamyard if the player chose Tepig as their starter. In both Pokémon Black and White and Black 2 and White 2, it can be found via Rustling Grass in Pinwheel Forest or Lostlorn Forest. Panpour can be obtained in Pokémon Black and White as a gift Pokémon at the Dreamyard if the player chose Snivy as their starter. In both Pokémon Black and White and Black 2 and White 2, it can be found via Rustling Grass in Pinwheel Forest or Lostlorn Forest.
In Pokémon Black and White, a Trainer in the Dreamyard will give the player the monkey with the type disadvantage against the player's starter Pokémon, which will have a type advantage itself against the monkey used by the Gym Leader of the nearby Striaton Gym.
Pansage can be obtained in Pokémon Black and White as a gift Pokémon at the Dreamyard if the player chose Tepig as their starter. In both Pokémon Black and White and Black 2 and White 2, it can be found via Rustling Grass in Pinwheel Forest or Lostlorn Forest. Panpour can be obtained in Pokémon Black and White as a gift Pokémon at the Dreamyard if the player chose Snivy as their starter. In both Pokémon Black and White and Black 2 and White 2, it can be found via Rustling Grass in Pinwheel Forest or Lostlorn Forest.
Source
Since you already have Pansear, to get Pansage and Panpour you need to either trade them or found via Rustling Grass in Pinwheel Forest or Lostlorn Forest.
Hope this helps!
yes, go into lostlorn forest to the right side of nimbasa city, and go into any shaking grass spots you see. You have about a 10% chance to find any individual monkey.