Before backing up content stored on an Aurender using a Mac, you will need to mount the Aurender as a shared folder on your Mac over your LAN (local area network). For instructions on how to perform this, please see the link below:
Copy and Paste from Aurender to Destination Folder
Once the Aurender is mounted to your Mac, simply navigate to the folder(s) you would like to backup, and Control-click (or Right-click) the folder(s) and select the "Copy" option (10).
Navigate to the destination folder or drive you wish to backup the contents to, Right-click (or Control-click), and select the "Paste Item" option (11). The contents on the Aurender will be copied to the destination folder, which may take some time depending on the speed of the network as well as the amount of content.