First of all you need a ISO image file for boot USB Pendirve.
If you don't have ISO Image file you can download here >> https://www.microsoft.com/en-us/software-download/windows10 (Note: Windows 10 ISO Image file).
Or You can…
imgburn is a awasome tools for creat ISO image file from DVD.
First Download imgburn here >> SetupImgBurn_184.108.40.206.exe ..
Then install process is very simple..
In this software they provide 4 excellent option.