Stockpile Punch Card is one of the new Punch Card challenges introduced in Fortnite Chapter 2 Season 3. Here's how to get punches towards Stockpile.
Punch Card challenges replaced Daily Challenges in Chapter 2 Season 3. There are dozens of challenges to do at your own pace. Completing a punch on a card gets you 14,000 XP for your Battle Pass. Some of the challenges, like Stockpile, reward you for doing things you already want to be doing in Fortnite.
Stockpile Punch Card: How to Complete the Fortnite Challenge
Stockpile tracks how much material you harvest. You'll earn a punch for Stockpile every at 1,000; 10,000; 100,000; 250,000; 500,000; and 1 million materials harvested.
These numbers are over time, so you don't need to harvest a million of something in a single game. You'll want to be harvesting as often as you can anyway, so you'll be sure to make a few punches from normal gameplay. Materials obtained from chests or kills also count, so you might fill this Punch Card up faster than you might think.
If you're on the Battle Pass grind, you just might be able to get to 1 million if you play a lot of games.