https://www.cnet.com/news/fortnite-season-6-week-7-challenges-and-how-to-complete-them/

Here are this week's leaked challenges that -- as always -- are subject to change by Epic Games when they officially reveal them on Thursday:

This is a challenge we've had before. On the surface, it seems easy enough, but I've had trouble finding seven ammo boxes in the past before the storm started closing in. Your best bet here is drop in to a named location and focus on it for a few games until you get it.