Separating MP4 files into Multiple Tracks

I am working with artists that have previously recorded material saved to MP4 files (not through Logic Pro). They want to revamp the old material and mix it better for an upcoming release. When the MP4 is imported into Logic, it’s all on one track. How do I separate the vocals from the beat? Looking to turn the one track into at least two or more to properly mix and balance the levels on both sides.