Miles wants to repair the hydroponic farms so his people would not be so dependent on trading. Unfortunately, the parts needed to repair the farms never arrived, as the person who was going to deliver them was ambushed by deathclaws.
Miles sends the Vault Dweller to Sammael, who hints at where the parts are. They are in the deathclaw playground, as Sammael stated. Toward the northeast part of the deathclaw playground the Vault Dweller can find the parts either on a corpse on the sidewalk or on the sidewalk itself (if the body has disappeared). The Vault Dweller needs to bring the parts back to Miles, who sends them to Smitty for fixing. Afterwards they should bring them back to the chemist to finish the quest.
Although Miles requests the specific set of junk, any junk can be used (such as that from Jake's house in the Hub) to complete the quest.
On very rare occasions, if the battle of Adytum is completed first, the scav NPC (who doesn't move) can end up in the doorway to Smitty's shop, causing one to be forced to make Miles do the work for them instead of ferrying the stuff around to Smitty's.