Nginx redirection

I am using nginx as my web server and have posted some links to it on Facebook. I have just changed my link from example.com to example.com/en/. Consequently, all the previous links will be unusable in Facebook, I would like to redirect all the example.com links to example.com/en.

My configuration:

server {

listen       80;
server_name  example.com;
charset utf-8;
access_log  logs/xxxxxx.access.log;

root   /var/www/html;

index index.php;
location = / { return 301 /cn/; }

location / {
    try_files $uri $uri/ /cn/index.php?q=$uri;
}
location /en {
    try_files $uri $uri/ /en/index.php?q=$uri;
}
location /my {
    try_files $uri $uri/ /my/index.php?q=$uri;
}
location ~ \.php$ {
    try_files $uri =404;
    fastcgi_pass   127.0.0.1:9000;
    include        fastcgi_params;
    fastcgi_param  SCRIPT_FILENAME   $document_root$fastcgi_script_name;
}
}