How to select two variables with the same random number?

Hello,

I have two variables ($ {townName} and $ {townId}), which contain all the extracted occurrences (name1, name2, ...) and whose number may vary.
I try to use two variables randomly ($ {townName_rand} and $ {townId_rand} which must correspond, to each towName corresponds a townId having the same index.
How can I randomly extract ($ {townName_rand} and $ {townId_rand} where rand is between 1 and ($ {townName_matchNr) and n must of course be the same for both variables.

Thank you.

Kind regards