Ranch Porch Foundation and Footing
It would be unusual for a contractor to build a monolithic porch, since that would waste a lot of concrete. The fact that the exterior of the porch goes down to approximately 48 inches below grade suggests that the porch walls may be built like a basement, perhaps 6 or 8 inches thick, and support the top of the porch. In any case, if the porch foundation is not adequately built to support a two story house, you cannot use it safely, so you are going to have to find out the details of the construction of the porch. This may require additional excavation.