or right click on the bar at the bottom of the screen select properties click on the start menu tab and then put a tick in the box that says "classic start menu".
it will change your entire start menu to the old style one complete with run.
if you don't like it like that simply repeat above and put the tick back in "start menu" restore it to how it is now.
Or right-click on start button choose properties , leave 'start menu' checked then 'customize' scroll down check 'run command ' . It will now be added to the start menu