Converting IP address to domain names using nginx in linux

I am trying to convert a test IP to a domain name using nginx on Linux I have created the file in /etc/nginx/sites-available and i have done using (ls -n..) the symbolic link and the file created has the following written on it

Server {

listen :80;

Server_name  example.com;

rewrite ^/(.*) http://example.com/$1 permanent;

}

Server {

listen 80;

server_name www.example.com;

}

My concern is when I reload my IP I keep getting the default page for nginx instead of the supposed changes

Can someone please explain why this is going on and thank you so much in advance