The calculated distance (air line) between Cheongju-si and Yŏnmu is approximately 41 miles respectively 66 kilometers.
By car or train, the actual journey to Yŏnmu is certainly longer, as only the direct route (as the crow flies) between Cheongju-si and Yŏnmu has been calculated here.
Air line (approximately)
66 kilometers
36 nautical miles