Arc or series of arcs -> Spline is easy. It is the "fit spline" command.
Spline -> series of arcs is a labor intensive task done by hand. Use the arc command, with the "three points on arc" option.
I wonder if there is a command or a macro to convert spline direct in a lot of arc......I don't believe there is not this simple comand in such program....
No there is not a command in SolidWorks to do this automatically.
Create 3 point arcs and lines, then add tangent or what ever other geometric contraints that are required. It will be ca lose but not a perfect match to your original spline.
It takes some practice to get an eye for how to do this quickly.