Can't print file as is

I recently obtained an STL file from a web site that has 3D print files for model railroading. The file

won’t print, even with supports, as it is a single entity composed of 310 objects, most of them are

floating in mid air. I tried to ‘split’ the file into objects, but can’t figure out how to group them and/or

place them onto the plate so they’ll print.

Any insist would be greatly appreciated.

Without seeing what’s going on it’s difficult to make solid suggestions, but I would probably open the file in a mesh editor to break it down into manageable pieces, then bring them into Studio.

3DBuilder is good, but you have to do some digging for that. There are lots of others.