Hello HelenR., welcome to the Microsoft community, my name is Luiz Cruz, an independent consultant and I would be happy to help you.
To create a USB flash drive with Windows 10, please follow the steps below:
Download the tool according to the installed Windows 10 architecture. On here: https://go.microsoft.com/fwlink/?LinkId=691209
Run the downloaded setup and click Create installation media for another computer;
Select the Language, then select the edition and architecture according to the installed Windows 10;
Connect the Pen Drive;
Click Next;
Select the USB Flash Drive option and click Next;
Click Finish;
Your thumb drive will be ready for Windows 10 installation, just boot it and install Windows 10.
Any questions, I am available.
See you!