Well, the core of the usage of HIMARS or MLRS system like that is to disrupt your enemy logistic.
First of all, there are virtually no way you can stop Russian from launching Artillery Attacks, as long as they have rounds and tube, they will continue to be doing so, the question now become how you can mitigate such attacks.
Now, you can do it in one of the two ways, target the main supply effort (or Main Line of Communication)or disrupt their region supply depots (The one that serve the immediate area). Both are each of their own. As I mentioned before, if this was me, and when I get my hands on MLRS like M270 or HIMARS, I will go after their Main Line of Communication (Kupiansk) , because you disrupt the normal flow of supplies, it will not stop the onslaught for now, since the "Ready to Use" stuff are already distributed, but it will hamper the supply effort, effectively your line of supply will be interrupted and will have a hard time filtering supply. That's very simple, you disrupt the supply coming from Russia, you increasingly lower the amount that supply get to the front.