This chapter of the guide to Dragon Ball Z: Kakarot has a walkthrough for Nam the Peddler side quest.
Time frame: From Attack of the Saiyans - Episode 2: Rumble with Raditz to Episode 2: Rumble with Raditz
Reward: 86 EXP, D Medal, Book for Grown-Ups, Fancy Urn.
Where to start: East Ravine Area, as Goku.
Talk to Nam and he will tell you about his problem. You need to talk to man nearby about the stone you found. Go to the person with the blue exclamation mark and talk to him.
You will receive new directions. Go to the dig site and talk to another man. Go back to Nam to complete the task. You will receive rewards, including Nam's Soul Emblem.