How do you get evee on Pokemon mystery doungene explores of darkness?

You can't get Eevee in Pokémon Mystery Dungeon: Explorers of Darkness. This is because Eevee is not a Pokémon that is available in this game.

Eevee was introduced in the Pokémon Mystery Dungeon: Red Rescue Team and Blue Rescue Team games.

If you are looking for a similar Pokémon in Explorers of Darkness, you could try to find an Espeon or an Umbreon. These are both Eevee evolutions that are available in the game.