Nintendo released its Consolidated Results for the Three Months Ended June 30, 2019 and 2020 and it revealed that Pokémon Sword and Shield have now sold a combined 18.22 million units and the DLC sold well.

Consolidated Results for the Three Months Ended June 30, 2019 and 2020

Turning to our digital business for dedicated video game platforms, sales increased as a result of the good momentum of downloadable versions of packaged software for Nintendo Switch, and also the popularity of The Isle of Armor, released on June 17 as part of Pokémon Sword Expansion Pass and Pokémon Shield Expansion Pass, the first-ever add-on content for the Pokémon series.Download-only software and Nintendo Switch Online also sold well, with digital sales reaching 101.0 billion yen (229.9% increase on a year-on-year basis).

Source: https://www.nintendo.co.jp/ir/pdf/2020/200806e.pdf

Pokémon Sales as of June 30, 2020:

Pokémon Sword and Pokémon Shield: 18.22 million
Pokémon X and Y: 16.45 million
Pokémon Omega Ruby and Alpha Sapphire: 14.27 million
Pokémon Sun and Moon: 16.18 million
Pokémon Ultra Sun and Ultra Moon: 8.77 million
Pokémon Let's Go, Pikachu! & Let's Go, Eevee: 12.20 million

Source: https://www.nintendo.co.jp/ir/en/finance/software/index.html