Carders use carding services, such as Cvvshop and Storecc, to get credit card numbers. These forums are often hidden on the dark web, which isn't indexed by search engines and can't be reached with a regular browser. There are tools available to check the credit card status.
Carders like Ccshop and Ccshopthen determine whether credit cards are active by visiting ecommerce websites and initiating many transactions. Carding can take many forms, with the most popular being a repeated use of a single card for identical amounts. Then carders use credit card holder's address as their billing address.