Hi karenamp,
The first place I would start is post #1 here which has all the basic information, steps, and guidelines you will need to make good choices … and avoid most of the worst ones like Kingsdown or other major manufacturers (or any manufacturer who doesn’t disclose the details of the materials that are in their mattresses).
Some of the better options and possibilities I’m aware of in the Detroit area are listed in post #2 here.
Phoenix