The calculated distance (air line) between Sv. Trojica v Slov. Goricah and Koper is approximately 125 miles respectively 201 kilometers.
By car or train, the actual journey to Koper is certainly longer, as only the direct route (as the crow flies) between Sv. Trojica v Slov. Goricah and Koper has been calculated here.
Air line (approximately)
201 kilometers
109 nautical miles