The easiest thing would probably be to call 3 Rivers, but this might help.
Run a strand on a given peg--mark or cut it.
Measure that strand. Depending on your technique, you should be able to subtract 14-16 inches from that strand and that number is the string length for that peg.
For instance, if your strand measures 74". Subtract 16", that leaves you 58". That peg is for a 58" string.
If the distance between the pegs is 1", then the string lengths are in 2" increments. If the distance between the pegs is 1/2", it goes in 1" increments--or you can check one more just to be sure.
I suggest marking your board by string length rather than bow length, because bows can vary. Some 62" bows will get a 58" string, some a 59" string, some a 60" string, etc.
Hope this helps. If you need string or serving material, or just have other questions, shoot me a p.m. or e-mail.