Scan Weapons Caches
You have to find two additional caches. The caches are spread randomly among the camps. Each cache will be marked with . If a camp doesn't have a cache, the camp might have one the next time Ryder visits. If a camp has a cache, SAM (or a squadmate) will comment on the presence of the cache.
When Ryder has found three caches, the mission will update to the next objective.
Someone has been hoarding weapons for an attack on Prodromos.
Search For The Message Source
The message source is from a nearby building. Outlaws are there. SAM detects explosives nearby.
Defeat The Outlaws
The Outlaws have two Hydras and reinforcements will arrive via airship.
Prevent The Shuttle From Leaving Kadara
Shoot the marked explosives next to the shuttle. This triggers the rewards for the mission.