wordpress.mydomian.com 404 Error

I have changed the root directive to server block and it works pretty well, special thanks to @RichardSmith, who have had mentioned the problem.
in case someone has the same Problem I will write a short explanation code.

server {
       listen 80;
       root /var/www/blog.mydomian.com
       server_name blog.mydomian.com www.blog.mydomian.com
       # the rest of configuration
}