Thread pitch is stated as 12 per inch. I just measured the screw from the rear license plate and it's 0.08" per turn, or pretty close to 12 per inch. I'm not sure if this is what's considered "coarse" pitch for the given screw diameter.
Hmm... that's a diameter difference of 0.1900" for the #10, versus 0.1969" for the metric M5. The M5 might be a little bit tight to screw in but probably close enough for government work; pitch being equal. However, if I read the thread pitch of the metric screw as being 0.8mm per turn, then that's way too small (fine). The screw I measured last night had a thread pitch of 0.08" or 2.03mm. Seeing as how 12 threads per inch works out to 2.11mm, you'd have to get a M5-2.1 screw if they even make one. I looked through the McMaster-Carr catalog and could not find a metric sheet metal screw with those dimensions. Largest pitch I see for M5 is 1.25mm for any type of screw.
Now, since I believe that the hole that the license plate screw goes into is actually a plastic insert, you might be able to get away with using a different screw pitch. But since the original screws have a wider pitch you could end up stripping the plastic receptacle.
Had a thought.... why not look up the part number in the online Parts database. Imagine this.... there's two different part numbers (and quantities) for these screws:
The first number in these strings is the part number reference from the diagram of the license plate assembly. The last number is the quantity involved. First line I decoded as being a SCREW, while the second line is a BOLT. Screw has a size(?) of "5xPT-12", while the bolt is definitely a metric "M5-0.8". This all seems to say that there's two different fastener systems used on the Model 3.
My car was delivered July 2018 and is a June build.
In the threads about the rear license plate there is evident a transition of how the plate is mounted on the back of the car. My car was delivered June 2020. I suspect yours has the previous mounting system while mine has the newer hardware. My hardware looks like this: Rear license plate screw stripped?
I miss my now closed True Value Hardware Store. They had the best selection of fasteners and people who knew them well.