World production is almost 20 million tonnes annually so that shouldnt be an issue. Its also not like electric cars use that much more copper than normal cars: normal cars have both a starter engine and an alternator plus all the engine wiring.

Also, electric motors can use aluminum wiring, and many induction motors have aluminum rotors since they can be cast at a lower temperature than copper.

So use aluminum, which has better conductivity per unit mass. And is essentially inexhaustible.

I wonder if we can "mine" all of the old copper wires (telephones, etc)?

It's actually a problem with people breaking into unused houses and ripping out the wiring. Or stealing other metal.

Scrap yards in my state (and I'm sure many others) are required to take identification from anyone that sells them metal.

Copper recycling can be quite profitable. Enough so that people rob houses under construction just to recycle it for cash.

There is a very lucrative black market in "recycled" copper. It's been known to be stolen off trucks by the tonne.