This challenge is part of the Remedy vs Toxin Mission that closes the first season of Fortnite Chapter 2. You'll have to search a total of 7 chests in landmarks in Apollo Island. It's not complicated as long as you know what a landmark is. They are those "intermediate" locations which names don't appear on the map. They can be monuments, hills, structures or singular buildings.
The only difficulty with this challenge is to find chests in these landmarks because some of them contain absolutely no loot — not even an ammo box!
Map
The E.G.O. outposts, the Power Plant or the Workshop are significant notable places — all containing between two and four chests. That's where you'll have to look to quickly complete the challenge!
We recommend that you complete this challenge in Team Rumble mode, especially during the week following its release. This will reduce your chances of running into warring enemies as soon as you land.