https://www.gamespot.com/articles/fortnite-weekly-challenges-all-objectives-for-seas/1100-6457737/

Season 3 of Fortnite: Battle Royale is ongoing, and each week brings a new set of challenges for players to complete. There's a free set of objectives for everyone to take on over the course of the season, but only those who purchase the Season 3 Battle Pass get to deal with the additional weekly challenges. These present players with specific goals to target and offer a path to quickly level up the Battle Pass and acquire its many rewards.

Fortnite week 3 challenges guide