The calculated distance (air line) between Kholmskiy and Rostov-na-Donu is approximately 177 miles respectively 285 kilometers.
By car or train, the actual journey to Rostov-na-Donu is certainly longer, as only the direct route (as the crow flies) between Kholmskiy and Rostov-na-Donu has been calculated here.
Air line (approximately)
285 kilometers
154 nautical miles