If you’re looking to complete the Galar Pokédex in Pokémon Sword and Shield, you’ll need to obtain a regular Persian that seems to be nowhere in sight.
That’s because the Pokémon is only available through trades in-game. It doesn’t appear in the overworld due to the presence of Galar Meowth and Purrserker. So first, you’ll need to grab a Kanto Meowth before you can go on your quest to get its evolution.
The only way to get a Kanto Meowth that can evolve into a Persian is through an in-game NPC trade with a little boy in the first gym in Turffield.
This is the only Kanto Meowth that can evolve into a Persian because the special Gigantamax Meowth you get through Mystery Gift can’t evolve. If you try to breed this Meowth to get more Meowths, the only thing that will hatch from the eggs are Galar Meowths. So this is the only Kanto Meowth that you can get.
To evolve it into Persian, just level it up to level 28 like normal and it’ll evolve, striking one more Pokémon off of the Galar Pokédex.