Someone else already mentioned, if you are just curious about your salt level, take a sample to the pool store, just don't let them talk you into adding anything.
In my opinion the only reason not to convert to SWG is the up front cost, you are basically paying for all your chlorine for the next 5-7 years when you purchase the system, but then you are not dealing with the inflation rate of the chlorine.
One of the big advantages of having a SWG is that you are constantly adding chlorine so you ppm is stable. When you add liquid chlorine, you get a spike when you add and the levels start to drop till you add more (unless you have an automatic feed system) .
Either way you decide, keeping chlorine levels at the 7.5% — 10‰ of your CYA, is the key.