Reply to Slide Potentiometers resistance...

Hi i am modding my midi mixer and would like to change the slide potentiometers. there are lots of them available however they all come in different resistances. how can i figure out what resistance would be the right one.
its a small usb powered midi controller. the cable used are really small, so i believe the resistance has to be really low. how can i measure the actual intensity and what else do i need to calculate the resistance. afaik its intensity I and power P which would be the easiest to measure.

Spannung U = Volt V
Stromst