The new games Sword and Shield Pokémon in addition to introducing new functions, they cut the Regional Pokédex, reducing to 400 the total of Pokémon featured in games. Some of these in order to be obtained need to be transferred from previous games.
Here are all the Pokémon obtainable via transfer
To get the following Pokémon you will have to rely on the application Pokémon Home (arriving in 2020), so that you can complete all the Pokédex.
Pokémon in Kanto
Pokémon di Johto
Pokémon in Hoenn
Pokémon in Unima
Pokémon from Pokémon Go
Sword and Shield Pokémon is available exclusively on Nintendo Switch.