The calculated distance (air line) between Munsan and Pyŏksŏng-ŭp is approximately 68 miles respectively 110 kilometers.
By car or train, the actual journey to Pyŏksŏng-ŭp is certainly longer, as only the direct route (as the crow flies) between Munsan and Pyŏksŏng-ŭp has been calculated here.
Air line (approximately)
110 kilometers
59 nautical miles