This page of the guide to Dragon Ball Z: Kakarot has a walkthrough for The Pilaf Gang's Plan side quest.
Time frame: From Attack of the Saiyans - Episode 7: Intermission to Evil Emperor Frieza - Episode 8: Intermission
Reward: 4,583 EXP, D medal, Brain Bread, Energetic Fish, Giant Fish Fin Muscle
Where to start: West Area, as Gohan.
The characters that you get the task from are standing at the entrance to the cave.
The objective is to defeat three robots. Even though the opponents are at level 16, they shouldn't cause you any problems.
Return to the quest giver to complete the task.