Where to Find and Catch Pachirisu
From Pokemon Go Wiki
Pachirisu are found and captured in Nest and Habitat locations.
Nests
Pachirisu Nests are locations that consistently spawn Pachirisu.
Habitats
Pachirisu Habitats are spawn locations where Pachirisu is likely to be encountered, but not guaranteed the way a Nest is.
Additional Tips and Information
Best Nests
If you know a really good nest or any of the nests above is really good, list them here: