Where is the screen mirroring button on an iPhone XR 14.0.1?

That got me to Screen Mirroring. However, I only get the spinning ball when I connect the phone to the TV with an adapter and a HDMI cable. I have tried two phone XR's and two different TV's and cables. I regularly use the same cable and connections on one of the TV's to do screen mirroring with a MBP without problems. Is a faulty adapter the problem or are there any other things I can try?

In "Settings>Control Center" I only find "Access Within Apps" and "Customize Controls". In "Settings>Control Center>Customize Controls" I find "Screen Recording" but not "Screen Mirroring".

You are right, I hadn't discovered the Control Center. Thanks for the help.

I mirror my MBP on my TV frequently with an adapter and a HDMI cable. Shouldn't it work with IOS with a Lightening adapter?

Thanks!!