The exchange quest unlocks at Stage 4. You can find it under the “QUESTS” tab on the main screen. 

In the quest, you can get Club Cards with a higher rarity (such as Legendary) by exchanging Common, Rare, or Epic Club Cards that reach the designated level.  The exchange quest will refresh once a day. The exact time when it refreshes can be seen by clicking on the “?” button in the top right corner of the quest.

By completing it, you will receive Perk and Quest Points.

Chest Cards Boost Perk:

To find this feature go to Quests → Perks → Advanced.

When completing the exchange quest, you receive Perk points, which are automatically upgrading Perk. The more you have upgraded your Perk, the more bonus cards you can receive from chests (except the fortune chest). As your Perk level is higher,  you will need a higher level of Clubs to complete the exchange quest.

Your Perk level is permanent, and it won't reset for each Challenge Season.