iMovie will import clips in order of their creation date. Once you get the clips into iMovie you can sort by date, name or duration. See this help link for more details on how to do it:
https://help.apple.com/imovie/mac/10.1/#/movdd0339f07
Also, in the media browser you can select a clip and adjust its date and time, and change file creation dates. Select the clip in the media browser and click on Modify/Adjust Clip Date and Time.
You don't need to copy your video files to your desktop before importing into iMovie. You can import directly into iMovie, or import into the Photos app and then access your videos from the Photos item in the side bar of an iMovie project. Also, from the photos app you can choose to export to a desktop folder in a sequence so the clips are placed in a particular order. I believe that the order will be preserved when you thereafter drag the clips into iMovie. But if it is not, you can sort by name or date as described above.
-- Rich