Travel by car: the driving distance between Nantes and Mostar is about 2.090 km which equals a travelling of approximately 20 hours. There is an option to go with the route via highway Germany or Italy. Driving distance in both option is approximately the same, but travelling time is little bit longer trough Germany. In Germany highway is free of charge.
Alternative ways of travelling from Nantes to Mostar:
Travel by train: it is possible to travel by train on this route via Paris and Munich where you change the train to Zagreb and then another one to Sarajevo and Mostar. More information about travelling by train in Bosnia and Herzegovina you can see here.
Travel by plane: there are no direct flights on this route; it is possible to travel only with stopovers in Munich, Vienna…
Map with buses from Mostar: