I want to make a surface in solidworks from a points cloud  (STL) that
was adquired from a 3d scanner, does anybody knows how to do it.

    Regards.
Marco

That's not really a CAD function.  There are other programs that can do
this, like PC-DMIS and Geomagic Raindrop.

Try looking up <www.geomagic.com>.  Perhaps they can direct you to
someone who performs this as a service.

I think it would be possible with SurfaceWorks (not sure, never used
it)

You could try next one. Create 3D Sketch and sketch the points cloud to
which you'll give the x,y,z coordinates. After doing that, "divide" the
points into sections which you'll use to create 3D curves. Then create
surface loft through those curves and use guide curves if necessary.