Are you talking about exporting from your iPhone an iPhone iMovie project, or just want to export the files themselves?
To transfer an editable iPhone iMovie project to your Mac use AirDrop to share the iPhone iMovie project (the project, not the individual clips) to your Mac. The project will appear in your Mac's downloads folder. Click on the project there and it will open in a Mac iMovie project, where it can be edited.
If you just want to transfer the individual clips, you also can do that with AirDrop. You would choose the share option of videos rather than project.
With AirDrop, you should enable AirDrop on both devices, and the devices need to be less than 30 feet apart.
-- Rich