How to dislodge bluestones sitting in cement? (Pictures)
They don't seem to be laid too deep into the ground: excavate the soil behind one of them and try to crank it up from behind with a bar. If it is feeling pretty solid you may have to break that few inches of concrete sitting in front of them with a sledge to loosen them.

Start from a corner or an end stone if you don't want to dig whole lot of soil.

If you can't move them this way you may have to use a jackhammer to open some space around them but I doubt it would come to that.