Just ran across this thread, so I don't know if you decided what to do with that NMO antenna mount, amazon link to a mount they sell.
https://www.amazon.com/3-4-inch-NMO-Mount-901102/dp/B0006VSHDK
As magimerlin said, it is very doubtful it will work for CB. You will find that style of mount in some municipal antenna installations and Ham radio antenna installs. There are a couple of reasons any antenna is mounted on the center of the roof, it will make the transmit and receive less directional, like a ground plane type of home antenna, it can 'see' in all directions equally, and the other reason is when there is direct contact between the ground part of the coax cable and the vehicle, it tends to work better than a magnet mount antenna. You can usually get a better SWR match of the antenna when it is attached directly to the vehicle.
As far as the coax you show in the picture, that is used in a lot of different types of antennas, not just CB, RG-58U.
http://www.ebay.com/bhp/rg58u-coax is an example...