How to import clips from one project into another in Adobe Premiere?
If you only need one of the clips you used in the old project, you should only import that one and don't even use the old project file. Locate the clip on your hard drive and import it into premiere, e.g. by dragging it onto the project panel. If you have trouble finding it, open the old project, find the clip in the project panel and right-click -> Reveal in Explorer.... That should show you it's location on your hard drive.