Not to worry, this is pretty regular stuff. I suggest you contact a home inspector that is a member of American Society of Home Inspectors (ASHI). Their national website will lead you to many reputable members in St. Louis. They typically offer radon testing as part of a home buyer’s inspection. I think the test requires the house to be closed for several days and undisturbed on the ground level of home (which is typically the main living level) during the testing time. If radon is found to be higher than 4 parts per billion, then abatement is recommended.
This involves hooking up a vacuum fan to pull negative pressure out of the cavity below the basement floor and blow/evacuate the exhaust outside the home. This process typically costs between $1,500 and $2,000 per fan. It looks like a PVC plumbing stack in the corner of the house with a small fan motor built inline. It’s pretty simple and connects with a 4″ round core boring through the basement concrete floor and exhausts outside the house at the floor level. I’m sure the ASHI inspectors can inform you thoroughly.