I have a b7100 with the b670 backhoe. The instructions I have for the 'attaching kit' says it will hook up to a 7100 or 6100 with the b219 loader (which I have). There are rails on the hoe that come forward to attach to the loader cross frame and some hanger brackets that you mount to the rear axle housing. Not sure if there are other ways to mount this hoe e.g. 3pt.
It is a nice little hoe, mine has the 16" bucket which digs fine in the soil we have around here. It only takes about 10 minutes or less to drop the hoe but takes about a while to re-assemble all the 3pt, hitch etc. parts back onto the tractor. All together it is about an hour to swap the hoe on or off.
I have it mounted on the tractor right now but will be dropping it today or tomorrow so if anyone wants pics let me know.
Charles