You can save a single image file of any video frame in your project.
In your Motion project, move the playhead to the frame to be saved, then choose Share > Save Current Frame.
Choose an image format from the Export pop-up menu.
To specify additional Motion-specific options, click Render.
For more information about options available in the Render pane, see Render Options for Sharing.
To see details about files to be output, click Summary.
Click Next.
Enter a name and choose a location for the saved file, then click Save.