I have node version 6.11.3 installed. I need to install 8.11.3 on windows. I just can't find anything that works. Does anyone know how to do this?
The easiest option is to just download the appropriate .msi
installer (x64 or x86) for the desired version. With each downloaded update, the newer versions will replace the older version. So for 8.11.3 you'd use https://nodejs.org/download/release/v8.11.3/
List of all versions can be found here: https://nodejs.org/en/download/releases/
However, if you want to be more flexible, you can give the windows version of NVM (node version manager) a try: