Change WordPress root directory in nginx

Mostafa Soufi asked:

I have a website that address is site.com and also a WordPress that is site.com/blog. I would change the WordPress root directory in the nginx.

here is my config:

server {
    listen 80 default_server;
    listen [::]:80 default_server ipv6only=on;

    root /var/www/html;
    index index.php index.html index.htm;

    server_name localhost;
    server_name site.com www.site.com;

    location / {
        try_files $uri $uri/ /index.php?q=$uri$args;
    }

    error_page 404 /404.html;
    error_page 500 502 503 504 /50x.html;
    location = /50x.html {
        root /usr/share/nginx/html;
    }

    location ~ \.php$ {
        include snippets/fastcgi-php.conf;
        fastcgi_pass unix:/run/php/php7.2-fpm.sock;
    }

    location /blog/ {
        root /var/www/blog;
   }
}

I getting the below error when I open site.com/blog

404 Not Found

nginx/1.14.0 (Ubuntu)