Cancel that order; that's an unbalanced cable. The mono cable for your monitors should look like a stereo cable because it's a balanced input.
Cancel that order, and buy two "trs balanced" cables. They look like this. If you buy cheap ones, you'll probably have to replace one within a year, but at the same time 4 cheap ones is the same price as 2 good ones.
I'd compromise cheap vs quality, and get two cheap Roland ones since they're a well-known brand.
Longer = worse for cheap analog cables. More room for places to go wrong.
Do you have any need to use a microphone? The Alpha is not a good option if you do, since it doesn't have a preamp with phantom power so cannot run a condenser microphone.
Yup! Those are wrong. Please report back when you get the right ones!
Here's an example of what you need:
See, it's 3 conductors; so the circuit can cancel external interference: https://en.wikipedia.org/wiki/Balanced_audio