When you access word online via https://www.office.com/ (selecting Word on the left hand side), with your list of documents, you will see the following icon:
You can upload any Word doc here and it will be added to your list and open with Word online.
Warning
Files on a USB drive are usually vulnerable to being intercepted by people without authority to access this information.
All they need is the USB drive in most circumstances.
This is why DSWs have online accounts, to keep this information in a secure store rather than in places where anyone can get at it.
Personal client information is highly confidential, and subject to stringent privacy laws. Staff should never save documents containing sensitive client information to a USB drive.