I don't think you can convert to those units without some other measurements. Conductivity does convert to SG easily if I remember correctly. Conductivity is simply a measurement of ion concentration. Nothing else. You can't determine without some other measurements the difference between any ions as you would need to know that for KH or GH measurements.
+1. TDS is approximated via conductivity (uS/cm) as said above. Some meters will allow you to switch from TDS to conductivity units. kH and gH are not all that contribute to conductivity. A separate testing kit is needed.