I am installing a double oven. The wires from the oven are red, black, white and a ground. The wires in the junction box are two black and a ground. All are 220V/240V.
What wire gets connected to what?
You will need to replace the wire from the electrical panel to the junction box. Your new oven requires a neutral (white) wire to power some 120v electronics in it. Your existing wiring doesn't have that - it just has two hot wires for 240v.