can not find Plugins Menu

Hi there,

I am newbie about wordpress and Would you mind to help me?

First I register free wordpress at http://www.wordpress.com (myblog.wordpress.com) then I upgrade which mean I regsiter my wordpress/blog (www.myblog.com), it takes $17. So, currently I have 2 blogs which are free blog and. Registered blog.
The problem is when I log in into my dashboard either using http://myblog.wordpress.com/wp-admin/ or http://myblog.com/wp-admin/, until now I can not find the Plugins menu which should be located between after Appearance and before Users.

Please help me and thank you.