How to redirect http://mydomain/blog/blahblah/ to http://mydomain/blahblah/ in wordpress htaccess?

I would like the htaccess rewrite rule to compare to IIS rewrite rule I tried which doesn’t seem to work:

<rule name="rewrite /blog/">
     <match url="^blog/([_0-9a-zA-Z-]+)/$" />
     <action type="Rewrite" url="/{R:1}/" />
 </rule>