I live in Canada, and have been unable to find cement mixing tubs.

I want to build a 3 tub high by 2 tub rat rack.

The tub I've picked is 16.9x34x13.7

How would I go about figuring out the dimensions and supplies needed?!

I'm not good with carpentry at all. My dad will be actually building the rack for me.

I'd buy a rack, but a 4 tub rack here starts at 250!!