The larger white and black cables come from somewhere under the cabinet I assume another stub up. The black one is what feeds the white one back out to the range. The large white one in turn was connected to the 240 and the old range.

The whole kitchen is on a slab, there is nothing ran into the wall, they all come from under the slab in pvc pipe. The breaker box outside has all the wires feeding into a large pipe I assume comes up into the house in that area somewhere.

 

Sure the old Jenn Air range worked because you were using a bare ground wire in the NM cable as a current carrying neutral conductor which has never been legal for an electric range. At the time the Jenn Air was installed, there should have been 3 insulated conductors; 1 blk, 1 red and 1 wht. The NEC changed in 1996 to require 4 wires; 1 blk, 1 red, 1 wht and 1 bare or green ground.

There is the problem, the new range requires a neutral conductor and you don't have one.

 

You should be able to tell by removing the cover of the breaker box and visually tracing the wires on the breakers to where they leave the box. If it is the conduit you think it is then that is how we may be able to wire for the new stove.

Assuming that is the correct conduit you are going have to dig a bit at the breaker panel to see where it goes. Does it go under the slab? Does it look continuous to the kitchen? I have a rough idea how to do this but can't start on guess. One other bit of info needed is that PVC conduit. If it is it is likely we can reuse it. If metal EMT less likely.

I have asked a lot of questions so I'll wait for the answers before continuing.

If the conduit does run under the slab or next to the slab buried and if the cables used are marked NM they were never code compliant and both the 120v cable and the 240v cable needs to be replaced. The good news is your breaker box is outside. That will make running new cable a bit easier.