The calculated distance (air line) between Klagenfurt am Wörthersee and Mödling is approximately 137 miles respectively 221 kilometers.
By car or train, the actual journey to Mödling is certainly longer, as only the direct route (as the crow flies) between Klagenfurt am Wörthersee and Mödling has been calculated here.
Air line (approximately)
221 kilometers
119 nautical miles