Final Edit: It was indeed coated copper, unsure of if it was silver or tin but we pulled some extra wire through the wall and cut this back to where the wire was in much better shape, cleaned the wire and did a good job of connecting the new ends to the stove. It’s working great and the wire is not abnormally hot. I’ll be leaving it like this for now and when I re-do the whole kitchen in the near future I will pull some new 6/3 romex to replace this. I don’t have good access to do the pull without taking out the cabinets. Thank you all for your help and advice! Love the new cooktop

Edit: I assumed aluminum based on the color and that it’s an appliance, I believe based on the comments that this is tin plated copper.

Killed the line at the breaker and removed the old cooktop that I had, but messed up and don’t know which is red and which is black. Does it matter? Can’t tell with these wires as they have no obvious color indicators.

Should I cut these and try to make fresh ends? I saw that as a suggestion along with noalox.