One of the Goals you can receive is to Complete X Trades. Trades are a good way to get rid of excess Cards and earn more Pilz.

Trades are offered by Terry, Dean or the Tron at the bottom of the map screen. They only appear once every couple of hours, and only if you have enough cards for the trade. How many cards of which type are needed depends on where you are in the game (main game, and each event is different).

It's up to you to decide if it's a worthwhile deal! If you don't think it's valuable, don't worry, they'll offer other trades in a few hours. Be sure to check out the deal even if you're just stopping in to open your timer crate!

You can also get Trades in Events!