DMX and XLR cables

[SoleJan]

Hello again,
so recently I found out that the existing cables in the school where I work with lighting and sound sometimes, has mixed xlr and dmx cables. The 'build in' lights in the auditorium are definitely dmx' as they've been done by a third party. But all other cables have been used for both sound and lighting. Now I know the difference between the cables is mostly their resistance, 120 ohm at dmx right?
I read online that meters and measuring that level of resistance isn't as easy (and I don't think we got an ohmmeter). 
So is there a way to distinguish these two (is there a reason to?). And yea, all cables are 3pol. 
I kinda want there to be some order.

Thanks
Jan