The calculated distance (air line) between Frýdek-Místek and Prostějov is approximately 57 miles respectively 92 kilometers.
By car or train, the actual journey to Prostějov is certainly longer, as only the direct route (as the crow flies) between Frýdek-Místek and Prostějov has been calculated here.
Air line (approximately)
92 kilometers
50 nautical miles