You might need DVD/USB install media to install it.
And, Prior to v1709 It was configured here by the system, but disabled in Device Manager. After 1709 and 1803 it was no longer here or showing in Device Manager because I had no Xbox connected any longer myself to my Modem/Router.
After V1709 & 1803 w/No Xbox connected prior to upgrade.
Right click on your Modem device Icon>>Properties in Network folder
Now look and see if it is at least configured for Teredo.
Before v1709 w/Xbox connected to Modem
Modem Device icon in network folder as shown above
You will most likely need your Windows install Media to install the Teredo service
You might have to reconfigure your Modem from Dynamic to Static IP and manually setup your PC's and devices for your network.