You can use this tool to quickly identify the size of your screws in case you sort them by size.

The available sizes are between M2 and M8 in 0.5 increments.

The numbers are easy to paint with a permanent marker for easy recognition.

If screws don't fit perfectly (but you confirm with a digital calliper that they're the correct size, you may need to tweak your flow rate as you may be over-extruding (or perhaps even under-extruding?).