There is no upgrade that you can purchase from WordPress.com that provides FTP access , the ability to install plugins, third party themes and software into free hosted WordPress.com blogs. If your require plugins you must hire a web host and set up your own WordPress.org install. http://support.wordpress.com/com-vs-org/
P.S. Note that typing in all capital letters in cyberspace is considered to be the rude equivalent of SHOUTING! into someone’s face.