Question: can you transfer pokemon from let's go pikachu to let's go eevee?
Answer: Only the Pokémon you've caught in Pokémon GO that were originally discovered in the Kanto region (as well as their Alolan variants) may be transferred. You can't transfer Pokémon from Pokémon: Let's Go, Pikachu! or Pokémon: Let's Go, Eevee! to Pokémon GO.