XPS 13 9370, No bootable devices found

Hi everyone, I've made a huge mistake and I don't know how to fix this. I attempted to dual boot my laptop with Ubuntu - this worked fine. However, on attempting to switch to Windows 10, it just restarts the laptop to bring me back to the Ubuntu screen. Ubuntu works fine, but my Windows is completely gone, which I need for college quite badly.

I tried downloading the Windows ISO on a USB and adding it to the boot list but this doesn't work. The laptop itself says no bootable devices found. Please help me!