On my pc screen it shows:
adb devices
- daemon not running; starting now at tcp:5037
- daemon started successfully
List of devices attached
A209xxxxxxxx device
So I do:
fastboot oem unlock 6bxxxxxx
and I get on the pc screen:
< waiting for any device >
and my phone is showing the following picture

Can anybody tell me what I have to do get the command ‘fastboot oem unlock 6bxxxxxx’ work?