You need to create a new game with the module, to get the cards. How game I made looks like: The instructions from the marketplace page: Quick Guide
Setting up the game
Dialect is a Roll20 module. To create a new game based off of the module, click on the Start New Game option from the site menu. The column on the right hand side of the page is titled Optional: Choose a Module .
Underneath this are thumbnail tiles for all the various Roll20 modules
that are available. For the ones you have purchased, mousing over the
thumbnail will make a check mark icon appear over the thumbnail tile.
Clicking on the tile will select this module to be used as the base for
this new game.
Accessing the rules compendium
The Dialect rules compendium is accessible from the web , as well as directly from your Roll20 game! To access the rules in-game:
Go to Game Settings from your game page. Under "Access compendium In-Game", select Dialect from the dropdown
menu. If you'd like your players to also be able to access these rules
(recommended), switch the "Share my compendium with players?" radio
button to Yes. You're all set! In-game, you can view all Dialect compendium entries by clicking on the (i) tab in the top right. .
Where are all the card decks?
Dialect comes with multiple card decks to be used throughout stages of
the game. You can show and hide these decks by going to your Collections
tab and toggling the Hide / Show option on each card deck. .