You don't want to convert anything to SketchUp if your intent is to print it on a 3D printer. The typical file format for 3D printing is STL. I've not heard of Ldraw, but Google answers all. I typed in "convert Ldraw to STL" and found many answers. One of them appears to be well received:
http://thehighproglow.blogspot.com/2...es-for-3d.html
As you can see in the link, it's dated 2014 which means there may be more recent, easier or more appropriate methods available to you.