just want to play my airs video on my 4k tv
Questions would be, which TV? If it has AirPlay built-in, you could use that. If you have an AppleTV, then as
@rJonze said, you can AirPlay to that. If you have a Chromecast device, you can download the Google Chrome browser and cast media from that to the ChromeCast device.
Beyond that, if you want a physical, wired connection, then most any USB-C to HDMI adapter will work. I’d recommend either Apples one, or any of the many adapters and hubs which Anker sells - a hub is a good idea as beyond HDMI, you also get USB ports, Card Readers, Ethernet and so on. A handy device to have.
Of course, almost all of the cheap and cheerful to expensive hubs and adapters will work as well. Many people use them day in, day out, without a problem. I personally trust Apple, Anker, Ugreen, Twelve South, Plugable, Belkin, Kingston, Satechi, Moshi, Caldigit and Wavlink to name a few.