All we want is a simple room with 2 sets of window.

That is subjective. Simple is 13x14? 20x15? 10x11? etc..

I updated the post. It’s 13x13. Thanks.

The issue is that the patio floor is not going to stay when you add an indoor living space , It will need to be done just like an addition. New footings poured just like a house , Where is the bathroom inside that will serve this new bedroom . You need to talk to an architect or a really good honest contractor to get some idea of the work involved . Is this bedroom a must have for your family ? In the midwest the footings will need to be done below th frost line and that could have some effect on the whole space above this . .