Config nginx for flask application (production)

Question

this is my first time production level on flask, I use the digitalocean tutarial for deploying flask-nginx-gunicorn on centos 7, I do that it's said

but when I what to do this command I got this error on terminal

nginx: [emerg] "server_names_hash_bucket_size" directive is not allowed here in /etc/nginx/nginx.conf:39
nginx: configuration file /etc/nginx/nginx.conf test failed

this is my myproject.service

[Unit]
Description=Gunicorn instance to serve myproject
After=network.target

[Service]
WorkingDirectory=/var/myproject
Environment="PATH=/var/myproject/myprojectenv/bin"
ExecStart=/var/myproject/myprojectenv/bin/gunicorn --workers 3 --bind
unix:myproject.sock -m 007 wsgi:app

[Install]
WantedBy=multi-user.target

and this is my nginx.conf

server {
    listen 80;
    server_name 158.255.74.33;

    location = / {
        include uwsgi_params;
        uwsgi_pass unix:/var/myproject/myproject.sock;
    }
}