You are probably referring to some forum post from many years ago, the scenery has been updated several times after that, so that update link is not required anymore.
With all our products, you don't need to worry about "updates". With FSX and P3D, we have a Live Update system which keeps the scenery always updated and, even if we don't have that in FS9, the full installer is always freely available from the Downloads page, and it's always the latest version.