They might re-order based on file name alphabetically and by number.
A tedious way would be manually add a prefix starting 01-picname.jpg - or better still 001-picname.
There is probably a way to partly automate this but for a modest number e.g. picture slideshow it might be no big deal.
You should be able to view the folder full of files on the flash drive - and sort/re-order by date etc - but that might still not get them how you want, and if viewing on a smart TV or other device, as mentioned in other replies it depends how that device is set up to view them.