If they’re being manually uploaded or if they’re being full imported then you can use the WordPress “Media Gallery” to sort them.
The fastest way to get there is to click the “Add Media” button above the content editor.
When that loads you’ll see two drop downs on the “Media Library” tab. In the first drop down select “Uploaded to this post”.
When they load you can move them around in any order you want and it should save the order as you move them.