I'm sorry if this question sounds dumb but it is okay if you use a movie other than the one in the score?
When I search a score I found that the movie is no longer available/downloadable so I think I have to use a different movie instead the one in the score

That's fine although the new movie you use will most likely be off sync so you will have to adjust the latency yourself.

Oh, thanks a lot. About adjust the latency you can find it when pausing the game and adjust it by press the R/L or ←/→ button.
(In case someone don't know about it)