With a bit of internet research, you can get some fairly reliable rules of thumb about ship size verses crew for fairly modern ships. Warships tend to be fairly low to the water and not have much space. These ships hover around a ratio of 2 crew for every 1 foot of length. If you go by that, and given the length of 134.5 KM which converts to 441,273 ft, then this ship would have a crew of about 882,546.
On the other hand, if you look at some cruise ships, they have a crew to foot ratio of about 4 to 1, including all the passengers. Going by that, you would get a crew of about 1,765,092. And that's not taking into account the amount of space some of those people take up with staterooms, and all the shops and dining rooms, etc.
Personally, I would say that the cruise ship figure would be better given that the general shape of the ship is more like a cruise liner than a warship, but that's not factoring in the internal hanger bays and such that this ship has either. Still, I think a crew of at least a million wouldn't be that far off either way.
As for the borg, yeah going by what is shown in the TV shows, Borg living space is about 7 ft by 1 ft by 1 ft, or 7 ft cubed. Doing some math, and going for the ludicrous point of borg ships being a thin walled cube full of nothing but people, and adding its 3KM a side, you could cram in 136,213,714,497 people. So adding back in all the stuff you need for a ship, I have no problem with Borg Cubes having 130,000 drones stuffed in there.