The calculated distance (air line) between Mülheim-Kärlich and Dortmund is approximately 78 miles respectively 126 kilometers.
By car or train, the actual journey to Dortmund is certainly longer, as only the direct route (as the crow flies) between Mülheim-Kärlich and Dortmund has been calculated here.
Air line (approximately)
126 kilometers
68 nautical miles