This is actually the Htacces rule:

RewriteEngine on
RewriteRule ^([A-Za-z0-9-]+)/?$ ir.php?id=$1

how must i pass it to some Nginx compliant rewrite rule... i just read the doc and did this:

rewrite ^([A-Za-z0-9-]+)/?$ ir.php?id=$1 last;

But didnt work. and the other question: Can there be any same as .htaccess to Nginx (per directory rules) Thanks

Being an response to your next question: no, there's no equivalent for Apache's .htaccess files for per directory configuration. You can have per directory configuration files incorporated through the master config, but Nginx will have to be reloaded whenever a config include file transformed.