Video path in Impress

How can I find out the path to a video file in my Impress presentation?

I created a presentation and linked some video files to it. Before I sent the notebook to ASUS service I formatted the disk and made a backup of all the files. Now there are question marks instead of the videos because the paths are lost. The files are all on the backup but impress will not find them, even when I run the .odp from the directory with all videos in. How can I find out the filenames of the videos in .odp and change the paths?
Thank you very much for any help!
LO Win 8.1 German