The calculated distance (air line) between Conflans-Sainte-Honorine and Metz is approximately 185 miles respectively 297 kilometers.
By car or train, the actual journey to Metz is certainly longer, as only the direct route (as the crow flies) between Conflans-Sainte-Honorine and Metz has been calculated here.
Air line (approximately)
297 kilometers
160 nautical miles