The procedure is for Windows machines. It will not help you if you want to connect a Plex server that is running directly on a NAS device.
You would need someone with experience with your particular NAS brand. Unfortunately I am not that person. I can only give you this: https://support.plex.tv/articles/204281528-why-am-i-locked-out-of-server-settings-and-how-do-i-get-in/
For now, you could connect the regular file shares of your NAS to your Windows machine. Which then in turn the Plex server on that Windows machine can use: How to add files on a NAS to a Plex library on Windows
