WordPress Username Format??

Hello Guys:

I am trying to comment on a blog and it is asking me to sign in with my WordPress username. I wasn’t sure what it was and then when I seen the format it was asking in, I was even more confused. It is wanting the username in this format here: https://username.wordpress.com

How do I find out what my real username is in this format? I do not remember seeing this format before otherwise if I have, I sure affected not remember it.

If anybody knows, I appreciate the answer and help!!

Regards,

RealEstateGuy89