Converting dryer from 3 to 4 prong cord but it doesn't have a grounding screw / wire
I'd try the screw above N for ground

It looks like the hex-slot screw going into the top center of the metal plate above the terminal block is your ground screw, so I'd land the cord ground there.  It doesn't need to be connected to a wire within the dryer, either: the cord ground simply needs to ground the dryer's chassis/frame to provide protection from electric shock.