QuickBooks doesn't store your client's full credit card information for security reasons. You can only export client details and the last four digit of their credit card information by running the Customer ContactList report.
From the left menu, click Reports and search Customer Contact List.
Click Customize, and go to the Rows/Columns section.
Choose the Change columns hyperlink, and put a check mark in the Credit Card # box.
Hit Run report.
I suggest contacting your client to get their credit card information updated.