There is this girl I like and I THINK she likes me back and I wrote her on Facebook. Is she interested?

Im 16 years old in high school and there is this girl that I really like and I believe that she likes me back and I would just like to know if she seems interested. I messaged her ln Facebook saying we shud talk more and all and asked her how she was doing an then she responded by saying "Hi! Im good. How are you Mr. Shannon(my last name)?"