Hi and welcome, elchoche!
As far as I know, there's no specific cable length that is preset if you were to buy them from J&R or Midget. I believe they come too long and you have to cut them to fit when you install them. Someone will correct me if I'm wrong about this and I hope they do quickly if this applies.
I believe, to install them, you would insert the threaded bolt just far enough so that you could get at least one adjusting nut on it and then run the unfinished end over all the pulleys to where it would attach to the top. Then, you should use something like a "come-along" to stretch the cable and tighten it over the pulleys. Check to make sure the cable is still properly running over the pulleys and then you can judge where to place the thimble and lock it in place with the swags. Finally, you can cut the excess cable off.
Install the cables one at a time, removing an old cable as you go. This way you won't mix up the different lengths.
I've not had to do this repair, so I may have posted some mistakes. Again, I think others will correct me if that is the case and I welcome it.
Hi-Lo 1707T - Tire Minder TPMS on Tow Vehicle and Trailer, 300W Solar Battery Charger, Equal-i-zer WDH, Progressive Dynamics Converter, Fan-Tastic Fan
2014 F150 Platinum 4x4 3.5L EcoBoost SCrew