Setting hollow STL file – Autodesk Community

The STL file is this one.

Let me start by saying that I only used Meshmixer, and I didn’t modify the file size. The first file, the one in photo 001, becomes 200 MB in OBJ format, while all subsequent OBJ exports only reach 15 MB, keeping inside all those shapes that would ruin the print. I’m sure it’s a wrong setting in Meshmixer, but I’ve been trying to export it with different settings all day, and I can’t get what I need.