Accidentally plugged in Arduino Uno before installing software, now it's not recognized by Windows 10, only powered by usb port
You do not need to install drivers in Windows 10 (unless you have a CH340G based Chinese clone, in which case it wouldn't have detected before installing the drivers). 

Windows 10 has its own CDC/ACM drivers built in - something every other operating system has had for years and Windows has only just caught up with them. That is why it detected COM3 fine before.

It should have worked fine without installing drivers. It may have been the IDE with the wrong port selected or something else interfering with the port that was stopping you using it.

Uninstall the Arduino drivers and revert to using the Windows built-in ones and work on diagnosing why it wasn't working with those.