While Hostelbookers and Hostelworld do not provide you with the credit card numbers, reservations from Booking.com should ALWAYS have credit card number attached.

To see if the reservation from Booking.com has a credit card number you have to click on it with your mouse two times, you should see such window: http://screencast.com/t/WSXq51vdNVN
Click on the "Credit Card Info " button and you should see the credit card number in the next window over here: http://screencast.com/t/GZZ90QivKh

If the credti card number is not there please provide us with the specific number of your faulty reservation and we will retrieve them for you