This mission is very similar to the previous one. Drive your Terrorbyte to the Vangelico store at Rockford Hills and deploy a drone. Carefully pilot it through the store and you will find a small security room at the back.
Look at the wall inside the security room and find an alarm controller. Use your drone's shock ability to disable it. Now you can enter the shop with your character and take the diamonds from one of the guards.
Finally, deliver the diamonds to the given location and get properly paid for another successful job.