24 or 26 AWG cable for my arduino UNO ??

fungus:
Only if it's multi-strand, not solid core.

I recommend spending $2 on some proper breadboard wires with pins on the ends.

I can't get wire with pins because the length is not standard in my project...

this is the cable i want to buy 3 wire 100' Twisted Cable - 3030_0 - Phidgets ....