The calculated distance (air line) between Sv. Trojica v Slov. Goricah and Maribor is approximately 11 miles respectively 18 kilometers.
By car or train, the actual journey to Maribor is certainly longer, as only the direct route (as the crow flies) between Sv. Trojica v Slov. Goricah and Maribor has been calculated here.
Air line (approximately)
18 kilometers
10 nautical miles