How are you intending to organise them? In the file system (finder), or in the photos app. I'll assume the photos app.
In the main "all photos" library view in the photos app, images are always sorted by creation date (and that is the image capture date in the exif data, not the file creation date). Do your scanned images have a capture date added by the scanner software? If so, they will be displayed in the order they were scanned in the all photos view.
In an album, and some other views, they can be sorted also by Title (which defaults to file name). So if the filename is numerically sequenced, then this sort will also work. Bear in mind though that this sorting is alphbetical, not numeric. So IMG10.jpg would appear before IMG2.jpg (1 is before 2). If you want title naming to work for sorting, then you'll need at least two preceeding zeros (for 500 images) so that you can use 001, 002 ... 010,011... 499,500 to keep the sequence.
Alternatively you can add date/time to the metadata if it is not already there in the order you need - either within photos using "adjust date and time" or with an external app.