* Denchu (電チュー) is a fictional creature from the Pokémon Mystery Dungeon series. It's not a real Pokémon species from the main Pokémon games.
* Raichu is a real Pokémon species. It's the evolved form of Pikachu.
There is no way to evolve Raichu into Denchu, as it's a fictional character from a different Pokémon game series.