If you’re unsure about the syntax of how to load a specific STL file into OpenSCAD, drag and drop the STL file onto the OpenSCAD program.
OpenSCAD will create a new window whose sole content is the STL import statement. You can then copy and paste that line into your own program.
Looking at some of the samples you’ve provided I would note that
1) There should be no colon “:” after “User”
2)It looks like you’re adding spaces in the path, where there should be none
import ( "/ Users / paolopuggioni / Desktop / miocubo.stl”);
import ( "/Users/paolopuggioni/Desktop/miocubo.stl");