I posted about this about a year ago citing the "Descriptive Road-Book to France" and you can find that post here
. Worth looking at if you find you're going to have a lot of these kinds of questions, since that particular book covers pretty much everything you need to know about traveling through France in the 1830's.
In answer to your question, though, Montreuil-sur-Mer lies on the Paris to Calais route, and would have been about 47.5 leagues traveling by road. Toulon to Digne isn't a direct route, but in some combination of other routes, the distance is about 22 leagues. Taking a carriage means stopping at posts along the road to change the horses which, on average, would happen once every ten to fifteen miles, so about every five leagues. By about 1800, coaches with travelers could do about 5 miles an hour, (whereas a mail coach could do more like 7). So when Valjean would have been traveling, assuming he traveled by public diligence, it would take about 28.5 hours to get to Paris from Montreuil-sur-Mer and 13 hours from Toulon to Digne. The journey could be non-stop - discounting the two minutes it took to change horses at each post - or he could have rested at inns along the way and then taken the next coach to travel through, rather than remain on the one.
He also could have traveled by mail, which was faster since the carriages were lighter and did not carry as many people, but this was pricier than taking the public diligence.
And there's always walking. A man on flat terrain -- a road -- can do about 30 - 40 miles a day walking at an average pace. It's more likely Valjean would have walked from Toulon to Digne, for example, which would be about a two-day's trip bar any meandering.