The Treasure Dealer is a menu of the game where you can obtain a special type of Items, required for expanding your town or completing some actions of the game.
To access it, tap on the icon "Ring Bell" at the bottom right of the screen:
In order to obtain the required items from the Treasure Dealer, you will need to fulfill orders by crafting and obtaining the indicated items as shown in the screenshot below.
If you’re unsure how to obtain an item shown, you can simply tap the icon and it should give you a hint.
Once you have all items required on a row, you can tap on the CLAIM button that will be appearing