I have refered the link given in reference and while using that command which is
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365
I have created key.pem and cert.pem so will it work fine or renaming can be a better option or should I delete it or recreate is it essential to have extension .key and .cert will pem not work