was the output format .mp4 or it was .png if it's .mpg4 the u can't do anything u have to re-render the whole animation. and if the output format was .png the start render form where the animation was got stuck.

Was the output format .mp4 or .png?

If it's .mp4 then you can't do anything, you have to re-render the whole animation.

If the output format was .png, then start rendering form where the animation got stuck.