Ring Wired Doorbell Screw

Hello. I purchased the wired doorbell (the cheapest one). I need to purchase self tapping screws as I am going into a uPVC frame. I cannot however figure out the proper size. Ring say “1-14” but I am assuming that is the length but need to know the head size so that the screws I order fit in the mounting holes. I’m not talking about the security screws I am talking about the mounting screws. I have attached an image. Thanks in advance.