Making cakes from pictures requires some business math plus some imagination. Here's an exercise for you to try. Those are cocktail size sausages in the bowl. Can you extrapolate from there?
The other way to figure the size: how many people is it supposed to feed? Because those are sheet cakes carved into the shape of the bowl and tank.
And the lid is anything that you can build with. I would use gelatin gumpaste because I could then make real hinges. You can use cardboard covered in whatever icing you can work with.
LOL-it's been 20+ years since I made one of these!! If I remember right, the "bowl" was layered rounds sized to the Wilton horseshoe pan(I used that as the "seat") (sorry-don't have it anymore so don't known the size). I know I just cut & stacked a couple of 9x13's for the tank and used cardboard for the lid. And had to have used buttercream as didn't know diddly about fondant back then (still don't ). Oh, and I used either snickers or maybe it was paydays candy bars...have fun-these always create a lot of laughs>