The marker for this mission is way down south from your home. Once you arrive, Rescue Lily's brother and his friend fro, the zombies. After the fight, you will receive a firecraker which you will use later.
Scavenge for loot around the barn first, then look out for the new survey point which is a farm silo outside the barn. Now use the firecraker on the marked area to help the brother's friend get some distraction. Just ride a vehicle with her brother afterwards and follow your way back home.