Any advice on how to remove these?

I have a fairly small backyard and I’d like to remove these concrete slabs (highlighted in red). The ground around (photo 3) contains good soil that is at least 3 feet deep and plants seem to take well to it. Does anyone have any idea how thick these slabs are and the best way to remove them? They look identical to typical sidewalk slabs, FWIW.

Im hoping that underneath them i can fill with soil since the building plans indicate there’s nothing there.

Also would appreciate any advice on how to engineer it properly so it drains where it should drain lol; I can provide more detail details on the rest of the backyard upon request).

Thank you!