If by the number of scenes you mean the number of video clips, images and audio objects used, this is available in a simple form in the Project settings dialog, under the Movie Information tab as shown below
Otherwise if you mean you have one long movie, eg a single long clip of different scenes, loaded into MEP and you want to know how many scenes there are or split it into scenes , there is the Automatic Scene Recognition function available under Effects, Video object effects as shown below, however this is not always perfect - more information is in the installed PDF manual available under Help.