hi, i'm not sure what you're looking for, but fir a start please see Set Adobe Flash to "click to play" on Firefox

Is the problem that audio or video autoplays on some sites even with Flash disabled? Because the likely explanation for that is the site is not using Flash for those functions. Flash definitely is not the only game in town for media: not only are there other media playing plugins, but Firefox can natively play MP3s and a wide range of video formats. Windows Vista and newer include Media Foundation, so using that, Firefox can even decode MP4 video. All without Flash.

Could that be the issue? Is that what you want to control?