On the docks of Aya you’ll find the enterprising Angara named Sohkaa Esof, who, after inquiring into the peculiarities of Milky Way trade customs will get around to asking you to complete a task for him. Seems one of his off-world suppliers went incommunicado, and he needs somebody he can cheaply coerce into checking in on it. That’s you. Agree to help him out to start the quest "Trading Favors".
While this quest may start on Aya (any time after your first visit) you’ll ultimately need to go to Voeld to discover what happened to his supplier. Once on Voeld, head for the navpoint, which is east of Hjara Station, near (southwest of) a Forward Station. In fact, you may have already passed by the site during the quest "Stage a Rescue". Whatever the case, head over there and investigate the camp; scan the Angaran corpse there and Jaal will recognize him as one of Sohkaa’s suppliers. Next scan the crates near the corpse for the missing supplies, and finally scan the ground south of the vehicle to find burn residue consistent with Kett weaponry. After the scan, you’ll be ambushed by the Kett so get ready.
Use the Nomad for cover if you need to. The Kett will fan out at points around the place. A sniper rifle can be used to pick off some of the weaker Kett. Use the vehicle for cover and pick off the Chosen one by one. After they’re dead, return to the supplies and recover them. Among them will be a Rare item like the Angaran Ranger Armor.
After looting the shipment, return to Sohkaa on Aya and deliver the weapons to unlock him as a new trader. He mostly sells resources, the most valuable of which being Titanium, but he’s also got a number of consumables. You’ll also get 530 XP for completing this little quest.