https://www.pcgamer.com/fortnite-shooting-gallery-locations/

It's the fourth week of Fortnite Season 6, which means new challenges await, and they keep getting better. This week, you'll need to get a score of three or more at some shooting galleries scattered around the map. Getting that score in a game of 50v50 or Disco Domination isn't too tough, but finding the shooting gallery locations in the first place can take time. Let's save that time and show you exactly where to find each shooting gallery. 

Once you're there, just stand on the small circle and look for targets. Shoot the ones that pop up, and quickly. Take too long and they'll disappear. Hit at least three and you're golden.