I have generally found that Live Aquaria ships at 1.019, but that may vary by species. They are one of several very major shippers and have a good reputation. They have a phone number, and you can call and ask, but ALWAYS check the bag water the minute you do open the bag just in case somebody didn't know what was going on.
They also include an acclimation guide which outlines what has been the standard acclimation procedure in the hobby for decades. The procedure I outlined above takes into account what their procedure doesn't---that a quarantine tank can be adjusted in ways a display tank can't. It is far, far safer and more comfortable for your fish to slip directly into a matching salinity and then to have the salinity raised over the next number of days --- evaporation is a nice, gentle way to have it done. (Salt doesn't evaporate: it concentrates). A qt tank should be unlighted, but heated, and well oxygenated, filter changed daily if not a cycled qt, and the water should be tested for nitrate, for ammonia, and for alkalinity daily. Nitrate should be low, not above 20; ammonia should be zero; and alkalinity should be between 7.9 and 9. I kee p mine preferentially at 8.3. Hope that helps. DO PUT A fine-mesh JUMP SCREEN on the qt: small tanks and scared fish often mean fish leaps. To lower nitrate, 10% water change. To stop ammonia, should you see any at all, Prime or Amquel brand water conditioner, and to adjust alkalinity, probably a water change, but you are unlikely to see that go weird. SHould you have an alkalinity issue in your tank, DKH Alkalinity Buffer is the fix.