As easy as it gets
Try typing the word 'missing' into project search panel. This should pull up the missing files.
To replace the imagery
Next Right-click (Windows) or Control-click (Mac OS) on the image that is missing in the asset window and mouse over "replace footage" and select "file" (Ctrl-h or command-h). You may need to use your search feature in Windows or the finder feature on Mac to locate the file.


