Psyduck is a Water-type Pokemon and is not available in Blue Rescue Team. The game features a limited selection of Pokemon, and Psyduck isn't one of them.
If you're looking to play a Pokemon Mystery Dungeon game where you can get Psyduck, you'll need to try a different game, like Pokemon Mystery Dungeon: Explorers of Time, Explorers of Darkness, or Explorers of Sky, where Psyduck is available.