This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for the Familiar Face side quest.
Time frame: From Attack of the Saiyans - Episode 7: Intermission to Episode 7: Intermission
Reward: 5,292 EXP, D Medal, Card 010, Fancy Urn
Where to start: Southeast Mountains Area, as Gohan.
To start this mission, you need to go to Goku's house. The quest giver is waiting for you in front of your home.
Your task is to go to the designated place and fight with the enemy. This fight shouldn't be difficult. The enemy has a slightly higher level than yours. After winning the fight, return to the man and talk to him.