mounting screws

I have AI Primes and Flex Mounts without any screws on them. Does anyone know what screws to buy to mount the Primes? I tried contacting AI but the rep told me he doesn't know what screw size it is and I should be able to get them at home hardware stores. I'm located in Canada fyi. Also what...

Does anyone have any idea what size these mounting screws are for the hydra 26? It’s the silver screw in the picture that mounts it to the bracket on the aquatic life T5 hybrid fixture. I just got a used hydra 26 to add to the two I already have and I can’t find the specs anywhere for the screw...