The calculated distance (air line) between Sv. Trojica v Slov. Goricah and Velenje is approximately 39 miles respectively 64 kilometers.
By car or train, the actual journey to Velenje is certainly longer, as only the direct route (as the crow flies) between Sv. Trojica v Slov. Goricah and Velenje has been calculated here.
Air line (approximately)
64 kilometers
34 nautical miles