How to transfer backups from the current backup drive to a new backup drive

My Time Capsule has filled up. I would like to attach an external drive to the Time Capsule and move one of the backups to the external drive (two macs are currently being back up to the Time Capsule). http://support.apple.com/kb/HT5096 says to drag the the folder "Backups.backupdb" on the current backup drive to the root level of the new backup drive. My problem is I do not have any file on my Time Capsule with the extension .backupdb. I only have files with the extension .sparsebundle.

What am I missing?

Roger