To restore from Time Machine you need to restore the iMovie library that contains the project. Projects cannot be restored independently.
However, you may not need to resort to a Time Machine restore. iMovie keeps backups of your iMovie library in an iMovie Backups folder. To get to the iMovie Backups folder, follow this file path from the Finder menu:
Go/Home/Library/Containers/com.apple.iMovieApp/Data/Library/Caches/iMovieBackups
When you get there you will see a list of previous backups of your iMovie library. Click on one dated just before the crash happene. iMovie will open in that library. Navigate to your projects browser (where your projects are displayed as icons) and see if your projects are intact.
-- Rich