How to access "developer console"? (Newbie)

I have connected a PC after a long time without using it. I chose the version of the other PCs, but something went wrong, and the versions weren’t the correct ones.

How could I massively restore previous versions?

I have read this Yet another way to restore versions in bulk and it seems what I need, but I don’t know how to run that jQuery in the developer console: After some hours searching how to, I don’t know how to access to that developer console, I am on Windows.

The developer console the guide refers to is a feature of your browser, not syncthing.

How to open it depends on your webbrowser, but it’s typically F12 or CTRL + SHIFT + J.