If you are referring to the mount that the rusty nut/bolt (in the middle of the picture) goes through... It is actually the rear mount for the drivers side wishbone.
You'll need to take the wishbone off to get to it.
You can get it pressed out and another one pressed in (or replace with poly) or just simply buy a new wishbone which will have the new mounts already fitted. Also, that will give you nice new front mounts on the wishbones too, as well as ball joints!