Bosley asks you to show him the completed Pokédex entry for Machoke.
The Request
Talk to Bosley in Cobalt Coastlands to accept the request.
Complete Machoke's Pokédex Entry
Machoke can be found in the Obsidian Falls area of Obsidian Fieldlands.
Reward
After you complete the Pokédex entry and show it to Bosley, you get 3 Grit Gravel and 1 Aux Powerguard.