How are the crt and key files created in /etc/jitsi/meet?

Hi folks, as we need rename the domain name for the hosting box, I’ve updated all configure files and also recreated certs using Letsencrypt for the new domain. But I don’t know how to recreate the following 2 files:
/etc/jitsi/meet/newdomain.com.key
/etc/jitsi/meet/newdomain.com.crt

I think these are the 2 files left to be changed, so that Jitsi can authenticate my host login info etc.

Many Thanks,
Clark

using openssl like this

It works! Many thanks Tanvir.