Assuming that Spire Albion represents a civilized world and a - more or less - democracy, they'd have roughly the UN recommended police to population ratio, which is 1 to 450, so 3000*450=1,350,000 people. Averaging 5700 per habble. Habble Morning, being the capital, is expected to at least double that, if not more, so roughly 12,000. Double again for habble Landing, being the center of trade, you get 24,000 people.

most authoritarian countries have more than that though. About 1:200 or even 1:120. That would leave the population at about 360,000-600,000 citizens.*

_{*Above statistics does not include cats. }