The Linksys MR7500 Hydra Pro 6E has one USB 3.0 port for an external USB storage drive.
 

To go to External Storage, log in to the LinksysSmartWiFi.com page first. Then, click on External Storage under Smart Wi-Fi Tools.

The following settings will be displayed:

• Node’s name — The node's name is the node that the USB drive is connected to.
• Eject — Tap on Eject to safely eject your hard drive.
• Drive data — When your drive is detected, the following section will appear with the drive’s name, space used, and total space of the drive. It will also display the IP address to use if you want to access your hard drive, which is the node’s IP address.
• The Refresh button — Click Refresh to refresh the page.
• Authentication — Tap Authentication to view information on how to access the drive for Windows® and Mac® computers. When accessing the drive, enable Authentication and create a username and password to access the drive. This feature is disabled by default. If you have several USB hard drives connected to several nodes in your network, the authentication applies to all your hard drives. 

Authentication requirements:

• Username - Minimum of four characters, maximum of 12 characters. The characters must be alphanumeric or include valid characters such as an underscore ( _ ) or a dash ( - ).
• Password - Minimum of 4 characters, maximum of 50 characters. The characters must be alphanumeric or include valid characters such as an underscore ( _ ) or a dash ( - ).

Make sure to click Apply then click Ok to save your settings.

If there is more than one USB hard drive connected to a child node that supports USB storage, you will see a list of drives from other child nodes.