This page offers a guide on how to complete Request 27: Help Wanted: Plowing the Fields in Pokémon Legends: Arceus (PLA).
This request can be picked up from Miller, who’s found at the farm in Jubilife Village. He’ll ask you to fetch him a ground-type Pokémon to help him plough another field for the farm.
Where to Find Ground-Type Pokémon in ARCEUS
The easiest Ground-type Pokémon to grab for the farm would be Geodude. They can be found in abundance near Deertrack Heights in Obsidian Fieldlands. They’re low level and easy to grab since you can teleport to the Heights Camp and walk a little down the hill to reach them.
Once you have a Geodude (or any other Ground-type - check a Pokémon’s types in their Pokédex entry), return to Miller at the farm and hand him over your chosen Pokémon. Upon completing this quest, you’ll have more fields available for farming! You can also switch out another Ground-type Pokémon at any time if you want your Pokémon back.