It appears that you copied a project folder from the Show Package Contents of an iMovie library, and then deleted or lost the library. Correct? If so, unfortunately, the project folder would need to be accessed in a new iMovie library through the iMovie 10 app before a new project could be generated from the project folder contents. If you have a Time Machine backup, you can try restoring your old library from the Time Machine backup and open the project from there. Restore the library to a different place than your current library so that you don't overwrite it.
If no success, or you don't have a Time Machine backup, try duplicating the project folder and then work with the duplicate. Open iMovie in a new library by holding down the option key while opening, and selecting to create a new library from the box that appears. Then go to your Movies folder on your Mac (Go/Home/Movies). You will see the new library's icon displayed there. Control click on it and from the drop down menu select Show Package Contents. A Show Package Contents folder will appear. Drag the duplicate project folder that you made into the Show Package Contents folder. Then go back to your iMovie app, close it and reopen, and see if you can open the project from there.
If no success, you can use the Original Media from the old project to create a wholly new project, but you will need to redo all of the editing.
-- Rich
