What drill bit for what screw tap?
If you intend to tap the hole, it needs to be &quot;a special drill size&quot; and you can look that up in any of a bajillion sources, many online.
Google says 2.5mm for M3 - I haven't bothered to check for actual charts, but it will likely be correct. Yup. That's for the usual cutting tap. 7/64&quot; for a forming tap.
If you just want the screw to pass through, M3 (i.e. 3mm) will do that.