Calculating equivalent plate properties for a foundation slab

Hello All,

I am trying to model a footing as a plate element in PLAXIS 2D. I have attached the figure I intend to work as follows.

I have two queries regarding to model is in PLAXIS. My actual foundation depth is 1.5m and the footing slab thickness is 1m. When I replace the foundation slab with plate element, should I place it on Level 1 or, Level 2? My guess is it should be Level 1. Also, for the equivalent plate properties, I have attached the following image of my calculation sheet. Please correct me if I am wrong with the calculation methodology for finding the equivalent plate properties

Thank you