ls /sys/class/net

In Debian and other linux distrobutions the network cards were always eth0, eth1, etc.

Since the arrival of the new release... Stretch, release 9, the name of the network cards has changed to somthing a bit more criptic. Not sure why. This may be a good thing but it doesn't look like it from my seat.

So, to find the name of the cards look in the /sys/class/net/ directory.