I would check some estimating handbooks if there are any around. They typically have data on this (tanks as a function of volume, heat exchangers based on area, etc).
Barring that, talk to a couple of tank constructors (Matrix, CBI, etc). 32,000 MT assuming 13m high walls would be close to a 60m diameter. If you know what you essentially want in the tank (material of construction, double bottom, floating roof, geodesic roof, etc), they should be able to give you a price pretty quickly. Granted, it will approximate but that sounds like all you are looking for.
Try a search on google for tank fabricators for other potential references.