Well generally Jordan retros aren't too wide or narrow when it comes to lacing, so depending on the pairs of eyelets the shoe has, so I'll give you the general length of shoelaces you may need to replace them.
6 eyelets : 40-46 inches (Jordan 3, 11, etc)
7 eyelets: 44-50 inches (Jordan 9, etc)
8 eyelets: 47-53 inches (Jordan 5, 6, 10, etc)
9 eyelets: 53-58 inches (Jordan 1(actual high-top), 2, 7, etc.)
I just took these off the top of my head, I may be wrong about the number of eyelets each shoe has, but just count the pairs of eyelets on the shoe you want to get replacement laces for.
Generally laces come in 45 inches, 54 inches, 63 inches, etc.. Pick the one that is closest to what you need.
It should be noted that this system is designed for lacing the shoe up to the top eyelet, and it's how factory laces are designed as well.