Unless you have another watch you can steal them from, it will be hard to say that they are "screw x".
You should be able to get those from a normal fastener supplier though. You just need to know the thread pitch, diameter, and length of the screws. You can measure the thread pitch with one of these: https://en.wikipedia.org/wiki/Thread_pitch_gauge
Note that metric and imperial systems measure screws differently of course, so if you're having trouble getting something that is exactly right, try using the other system. Googling around should get more details on getting the right measurements.
I have the above watch that has four small cross head screws holding the back of the case on.
My question is that these look rather worn so where are places to get these screws and what measurements would be needed?
The pic is not the actual watch but is the model.
.. on the other hand, there is the ETA 2893-2 automatic GMT for example...