Time Capsule.

If you want to use that drive as network storage, plug it into the Time Capsule's USB or Ethernet ports. If you want the drive's content put on the Time Capsule, drag, clone, or image it. If you want the drive's content backed up on the Time Capsule, ensure it's not excluded in the Time Machine pane of System Preferences.

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If you want the drive's content backed up on the Time Capsule, ensure it's not excluded in the Time Machine pane of System Preferences.

And the drive must be formatted for a Mac, and connected directly to a Mac, not the Time Capsule.