The calculated distance (air line) between Shaykh Miskīn and Tadmur is approximately 171 miles respectively 275 kilometers.
By car or train, the actual journey to Tadmur is certainly longer, as only the direct route (as the crow flies) between Shaykh Miskīn and Tadmur has been calculated here.
Air line (approximately)
275 kilometers
149 nautical miles