Convert line segments into continuous spline or polyline

I need to create some spur gears and a rack gear with accurate tool profiles. MITCALC generates a dxf which I can copy and paste into a solidworks sketch, however, the sketch consists of thousands of line segments. I would like to convert them into a continuous spline or polyline either in Solidworks or Draftsight.

Can anyone tell me if and how this can be done?

Thanks

SolidworksSketching