What wires are connected to the "Range" disconnect/pull out?
Would it be the Central Unit & where do they need to be attached on the New Breaker box, maybe to a 50 amp breaker?
There is not a chance that the Service from the pole is attached to both the meter & the conduit coming from the top of the fuse box is there?
Sorry, but if you have to ask those questions you are in way over your head.
If you can't determine where cables go, where they come from, and what they do, if you don't know what wires get attached to the "Range" disconnect, you really need an electrician.
The way you describe it this would not be an easy upgrade. Get an electrician.