So… is your Plex Media Server running on the Windows machine (with the media stored on your NAS) or is the Plex Media Server installed on your NAS (same as the media)?
PMS running on Windows
To update the PMS running on Windows, download the correct installer from https://www.plex.tv/media-server-downloads/ – make sure to pick the package for Windows (direct link for the current public release). When the download is completed, stop the existing PMS and run the installer.
PMS running on FreeNAS
If you want to update PMS on the FreeNAS, you depend on how you installed the app. If you installed the plugin from their Plugins section, you’ll need to wait for the update to make it to their repository.
It’s technically possible to access FreeNAS on a terminal (e.g. via SSH) and to manually install Plex (e.g. from an alternative repository (e.g. manually installing the FreeBSD package you had downloaded on your machine – this will however require some more specific technical knowledge).
