Can I export the first 6 and last 4 digits of a customer’s credit card?

Yes, both the Transactions and Billing Information exports contain the fist 6 and last 4 digits of a customer's stored card. You'll be able to obtain the information that you're looking for from either of the exports moving forward.

The account_code column can be used to combine the exports and ensure that the numbers match properly for each customer account.