Pokemon Legends Arceus What A Massive Mushroom Request

Where To Find Request
From the Research Board after you catch Parasect. (You can also Evolve to obtain)

How To Complete
Speak with Morel in the village, and deliver the Parasect to complete the Request.

You can find and catch Paras, Parasect at the locations listed below in PLA.

Obsidian Fieldlands (Nature's Pantry)

Crimson Mirelands (Golden Lowlands, Diamond Heath, Cloudpool Ridge, Cottonsedge Prairie)

Cobalt Coastlands (Windbreak Stand)

Coronet Highlands (Heavenward Lookout, Wayward Wood)

Evolve Paras