No, TimeMachineBackup is designed as the target folder for Apple Time Machine backups (Time Machine is Apple’s built-in back-up program on Macs).
What you need to do is create a new share (from the ribbon menu on the MCM dashboard, select shares and then the folder/+ icon to make a new one). You can name it what you like, and then either make it public or private (and if private grant the users set up on your MCM either no, read-only or full read/write access).
The new share will then appear alongside the existing ones (Public, Smartware, TimeMachineBackups etc) and you can use it as your target folder.
One other point, your transfer from the USB to the NAS will be a one-off, not a recurring thing. So the copy or sync won’t happen unless you trigger it. There are ways to hack the NAS to make it automatically repeat using Cron - see this post for details on how to do that. Note it involves SSH and altering the MCM’s internal set-up, which may well invalidate your warranty.
