This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for The Fifth Trainee side quest.
Time frame: From Attack of the Saiyans - Episode 3: Survival 101 to Episode 3: Survival 101
Reward: 376 EXP, D Medal, Bronze Compass, Beast Meat, Chicken
Where to start: Central Plains Area, as Piccolo.
To start this mission, you need to talk to Yajirobe. He will ask you to provide 6 deer meat.
After killing 6 deer, return to Yajirobe. This will complete the mission.