How to fix the cable connection between a Siemens hob and oven?

I have a Siemens Ceramic hob and Electric oven - there is a Main power connection (Poly box) which is fine, but there is also a small connector with 3 identical black cables - The connectors for this connection are missing, so there are just 3 thin black cables coming up from the oven to connect to 3 thin black cables on the hob part. I can install new connector but:
Q1. does it matter which of the cables connect to each other? If not, how can one find out which is which?
Q2. What are these cables for?

Thanks in advance for any help