The calculated distance (air line) between Mirna Peč and Slovenj Gradec is approximately 45 miles respectively 72 kilometers.
By car or train, the actual journey to Slovenj Gradec is certainly longer, as only the direct route (as the crow flies) between Mirna Peč and Slovenj Gradec has been calculated here.
Air line (approximately)
72 kilometers
39 nautical miles