I have 3 mpeg2 files that I am trying to split into smaller parts

All 3 files are from a DVBs card. The sizes of the files are 735mb, 4.60GB and and 6.34GB

I am using a mpeg2 cutter program but it is telling me the files are not true mpeg2

I have looked at the software avilable on this site but getting confused.

What software will be the best for me for converting all the 3 files into true mpeg2 so I am able to cut them in my mpeg2 cutter program?