Replacing old with new

Your new one needs the newer 220 volts supply.

https://ask-the-electrician.com/wiring-options-for-a-kitchen-oven.html

https://www.google.com/search?q=wall+oven+consists+of+4+wires+white+red+black+and+green

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Simply put, it won't work. New oven=white is neutral, black and red are power but not on the same "leg", and green is ground. If you use a meter, black and red should give you 208-230 or so volts. Wires from wall=White is neutral, blank is voltage (probably 120 or so volts) and bare copper is ground. The dual voltage plug can be used for either 125 or 250 volts, not both as required by the new oven. Need an new circuit pulled and wire/breaker matched to new oven power requirements.

where I can purch a second unit

Your copper, green wire are the ground. I beleave that the white is the power, and the black is your neg. to make sure i would use a wire tester to determen the power. From there white goes to white, black to black, and green to copper. I am not sure on the white/black wire it maybe another power. Look at your instalation manual it should tell you.
Hope this can help.

I've tested these timers.
Here's what to do:
1) Connect green to bare copper
2) Switch has 2 wires. For now, connect these two wires to timer-black and timer-red. Choose either one.
3) In back of wall box are white neutral wires twisted together and covered with wire nut. Timer-white wire connects to these white neutral wires. This action gives power to time clock.
4) If wall box does not have white neutrals described above, then connect timer-white to bare ground wire. Bare ground connects to neutral busbar in breaker box.
5) Turn on power and click manual override button or switch. If lights turn on, timer is wired correctly. If lights do not turn on, then reverse timer-red and timer-black wires.

Manual for GE 15265
http://waterheatertimer.org/pdf/GE-15265-manual.pdf
15A timer works fine on two bulbs, up to 1440 total watts.

If old switch has 2 screws plus green ground screw, then timer is right.
If old switch has 3 screws plus green ground screw, 15265 doesn't replace 3-way switch.

Timer-green wire connects to bare ground wire

Old switch has 2 screws with wires on each.
One wire is Hot-from breaker and this connects to timer-black wire.
One wire Goes-to-lights and this connects to timer-red wire.
If you get these two wires reversed, timer will not work, so reverse them.
It will not blow circuit if the timer-red and timer-black wires are reversed.

Timer-White wire is the confusing wire for everybody:
Timer-white wire runs clock motor located inside timer.
In back of electric box are neutral white wires that are twisted together and covered with wire nut.
Connect timer-white to these neutral wires.
If box does not have neutral white wires, connect timer-white to bare ground wire.

http://www.manualsdir.com/manuals/400481/ge-in-wall-15086-ge-smart-digital-timer.html

The wires on your new switch are intended for black = power .. white = neutral . and red = lights .. with two black wires on the old switch I am assuming that there is a bundle of white wires in that wall box, the white timer needs to join that bundle ... then you need to determine which black wire is the power from the electrical panel ( voltage tester) and connect to the black timer wire .. the red timer wire connects to the other black wire in the wall..

Please Vote !!

if you have a electric meter check the voltage coming out of the wall to be sure it is 220 v???? (meter across black and white)then with your meter only test black wire to ground and white wire to ground seperately you should have 110 from each wire to ground?
If you have only 110 to the black and no reading on the white, you either have a bad breaker or a 110v circuit
If you read 220v and you new heater is rated for 220v black to black and red to white wall thermostat or built in as long as you have 220v to your connection from the wall or your wall thermostat when turned higher than room temp.
Bare grounds tie together and mount to your green ground screw

what is the make of the thermostat? are the heaters 240 volts?