Pro Tip for others ordering parts or accessories (expansion cards, upgrades etc.) buy a pack of the mainboard and chassis screw packs (yes they are two separate packs). They are only a few dollars and will be invaluable if a screw is misplaced, or breaks off, or disappears mysteriously when you swore you had them all set aside! Many of these are not available locally.
I think the chassis should’ve included the screws but there were some other reports that their screws were missing, too. So I would message support if they could send you the screws for free.