I had to look up where the bus terminal is now, because it has moved since we used to pick up my great aunt and uncle coming in from the boonies on the edge of Alsace. I see that it is now on the back side of the train tracks behind the Pompidou Centre.
I am sorry to say that neither one of the seems to be in a very convenient location, but at least the first one is not in the middle of nowhere. The second one would certainly be lovely during the warm season since it is on the waterfront. Both of those sites give bus stop information in the "access" link. They are both just one kilometre from the train station (which is not far from the bus station), but you would have to be particularly intrepid not to take a wrong turn on all of those crooked streets at odd angles.
It might be an appropriate time to spring for a taxi.