How can I use a multimeter to find out how many OHMS are in a cable?

Measure the potential difference (V) across the cable and the current (I) running through it. Then use Ohm’s law: V = IR. R is the resistance, given in ohms, where 1 ohm is 1 volt divided by 1 amp.

What @Ivan said. Remember Ohm’s Law, it’s the basic law of electronics.

You can fine a 10 dollar multimeter at radioshack. Turn it to ohms and connect the cables to both sides.

Others have covered the multimeter question, as to where to find the cable find a Graybar or similar com/data distributor nearby, RadioShack may carry that as well.

Remember when you use the meter you need to connect it to the same conductor on each side of the cable and dont touch the cable or exposed probe. Also touch the probes together before you meter and make sure you dont have some crazy reading (Should be really close to 0).