that's pretty direct :
1. Evaluate the cost (fixed and variable) to build and run the mall. Probably function of the number of square meter built
2. Evaluate the revenue model. In case of a mall, I assume revenue are maily generated from rental of floor space to stores and brands
3. Calculate break even. In this case it would be to evaluate the number of square meter to rent at price detailed in 2. to cover the cost described in 1.
Let me know if you need more details.