How do you see your device because I can’t see it on screen mirroring

You must make sure that the device you are trying to Screen Mirror with is on the same Wi-Fi network as your iPhone. You also need to make sure that the device supports AirPlay.

If both devices are on the same network and you know it supports AirPlay, try restarting both devices.

You can find more information here:

If screen mirroring or streaming isn't working on your AirPlay-compatible device - Apple Support