The calculated distance (air line) between Deir ez-Zor and As Salamīyah is approximately 176 miles respectively 283 kilometers.
By car or train, the actual journey to As Salamīyah is certainly longer, as only the direct route (as the crow flies) between Deir ez-Zor and As Salamīyah has been calculated here.
Air line (approximately)
283 kilometers
153 nautical miles