I looked it up and think you mean this one:
Galdon class cruiser
The download provided is a zip file. Unzip it and it will have a Galdon Class Cruiser folder. Just drop that folder into your Star Made blueprint directory. You can then use the ships catalog to export it as a sment. The blueprint will then be in smd3 sment format.
If you really want to export as smd2 sment format then you need to install a version of StarMade from before the Chunk Update.