You could take out another similar screw to use as a template. If you have a range of nuts to check the thread ok, or use a thread gauge if you have one. If getting new the stainless/ locktite tips are good.
Thanks a lot for the quick replies! As everyone seems to agree that they are metric, I will take a look at a local DIY here in Switzerland. They should be able to help me out. best of regards,
