They are torx screws and you'll need torx screwdrivers as well. It's a good idea to have a set of torx screwdrivers as most screws in the car are torx. You should be able to get them at any store that carries screwdrivers. They're not overly common but definitely common enough that you should not have trouble finding them.
I know I had a hell of a time finding the proper screws for my license plate. I'm no mechanic by any means, I don't keep a large supply of screws. There are a ton of people on here that have a vast amount of knowledge so don't be afraid to ask a question you may think is dumb.
Mine didn't, just checked with the spare tire, but I ran to autozone and they hav a really nice display where you can check the width of your screws and I was able to find ones that fit my license plate cover and bracket perfectly even though they are metric.
Just a follow up - you might want to also buy a set of torx bits. I got some smallish ones at harbor freight that fit into a 1/4" socket. The screwdrivers are great for things that aren't in too tight - I find the screwdrivers are faster to use than a ratchet, BUT sometimes you run into something that's in pretty tight or an odd size that doesn't match your screwdrivers.
But Harbor Freight will be 1/3 the price of Sears. The last time I was at Sears Hardware was to buy a 6" 1/2" extension - they wanted $10.99 or so. So I went to Harbor Freight and bought a 2' 1/2" breaker bar for $8.99 and the 6" extension for $2.00 or so. That was the last time I was at Sear - over two years ago... Ron