Do you mean 3 inches?
I've never seen the tool for sale to put this IDC connector on. IDC = Insulation Displacement Connector. They work by piercing the insulation to make contact.
I've redone IDC cables, but only up to the 40 wire kind. I did it to add space between the two drive connectors. Since I see you got no replies, I'll describe my experience. Basically, pry them apart starting with inserting something thin like an Xacto knife. Some cables have a strain relief that has to be pried off first. You can see a small loop of cable that wraps back under it. The plastic nubs that lock the strain relief and cimp-on on are tiny and one-way, not designed to be removed. Most often you break at least one of the nubs. (Some have metal clips instead of plactic nubs to do the same thing. But the metal clips tear through the plastic or bend as you pry them off, so they don't really work afterwards either.) The strain relief is useless in that case. But the wire connector part works. Sure, its ugly and shody. But the 40 pairs of wire-piercing prongs hold so strong that it hard to get the cable off them once you get it on. Or you can buy new IDCs, which ARE around (or were.)
IDC Female Connector 80 Conductor for sale
To put the connector on, just line up the two parts of the IDC with the wires, squeeze enough to get it started, and squash (gradually) together in a vise or with a C-clamp. If you are just going to do a couple, there is not much use in a specialty tool which would actually do the same thing.
edited:
An IDC crimper up to 68 wire