The calculated distance (air line) between Gereshk and Lashkar Gāh is approximately 20 miles respectively 31 kilometers.
By car or train, the actual journey to Lashkar Gāh is certainly longer, as only the direct route (as the crow flies) between Gereshk and Lashkar Gāh has been calculated here.
Air line (approximately)
31 kilometers
17 nautical miles