I think they will need an energy source, matter to build their bodies and ships with as well as some kind of preparation in order to be able to digest or work that matter and thus, places where facilities to turn matter into a useable form exist. And those places will be important to them.
Well yes, and to some extent that is how some issues have occurred - when other species have unknowingly (or knowingly) strayed into those regions and interfered.
Big questions though about how it is in terms of their civilisation as a whole. For a loosely comparative example, if a human mining company’s operation in a few systems got disrupted, what would that mean in terms of the entire human civilisation?
Having said that, it’s difficult to say how useful that kind of comparison is. Human civilisation has only been interstellar for 1,000 years or so, whereas the Thargoids have been an interstellar civilisation for more than 2,000,000 years (and we’ve got no idea just how old their civilisation actually is).
After all, if they don't need anything, what would be their motive to interact with us at all?
Theories abound on that matter!
There could be a multitude of reasons. They might need things beyond the basics of survival. They might just want things. They’re aliens though (as opposed to a re-skinned version of humanity, or aspect of humanity, to look at in more meta terms), so we don’t really know to what extent we can apply standard human conceptual frameworks.
Just to come back to the first matter from the post, we know that Merope, and Merope 5 c in particular, is in a sense important to the Thargoids, as it’s used as a reference by the Thargoid Sensors, Probes, etc. What we don’t really know is why.
Similarly, why is Col 70 Sector FY-N C21-3 referred to? We (in the sense of independent pilots) just don’t know. Though unless the permit locks are hard enforced by an external non-human force, then some within humanity do know what’s there.
It’s on the boundary of the Braintree field which surrounds the main Guardian bubble, but whether there’s any significance to that is a matter of hypothesis and speculation as it stands.