If you're looking for a meeting place or a good stop around ½ or halfway between Castelfranco Emilia and Mantova, you can try Carpi, Italy, which is about half an hour northwest of Castelfranco Emilia, or about half an hour south of Mantova.
About ¼ or a fourth of the way, you can stop at Modena, Italy. This is about 17 minutes northwest of Castelfranco Emilia.
If you drive straight through without stopping at all, the total distance is 92 km. The distances shown above don't include local roads to get into each town, so if you're planning a long road trip, make sure you factor in traffic and road conditions, rest stop breaks, and interesting detours along the way. If you're in a rush, you can do the trip with zero stops, and your total travel time would be around 1 hour, 6 minutes.