Hi and welcome to FixYa, I am Kelly.
What is the model number so I can look up the installation procedures for THIS oven?
Usually for a 3 wire connection it will be connected as follows:
1 WALL black to the left terminal block terminal
The bare copper wire to the center terminal of the terminal block
2nd WALL black to the right terminal of the terminal block
See this picture link:
If you notice in the picture it shows a black red and white connection.
Red = black for your connetion 115VAC
White = bare wire neutral Ground
Black = 2nd black for your connection 115 VAC
When the power is connected properly and using the house wires as a reference if you are
reading it with a meter you would read EITHER black wire to the bare wire = 115 - 120VAC
Reading Black to Black = 230 - 240 VAC
If you still have questions feel free to respond here and I will gladly help you.
Thanks for choosing FixYa.