Start with this: https://en.wikipedia.org/wiki/Mars_Colonial_Transporter
and make it bigger and longer.
The entire colonial transporter maybe waiting in the orbit, and what we saw was just passenger launchers waiting to be integrated into the main colonial transporter.
for generation ship size, maybe we can start with this concept:
http://gundam.wikia.com/wiki/Space_Colony
The average size of an open-type cylindrical colony is 6.4 km in diameter and 36.0 km in length.
But this is, again, insane. How could sponsor which supposed to be short on resources built such giant ship. Comparing to other seedships, which, i think is 1.5-2 km long.
Also, i don't think that they transport resources from Moon, Mars or something else. They have no mines there. I remember that daming mocked at the conference that they construct only a settlement on for a year or two. But also it was siad there that it would be better to spend resources on mining interstellar bodies rather than seeding.
So i think that they don't have a developed mining facilities on other planets in solar system.