I have some movies of the kids/cartoons which I want to split.

Just split ... nothing fancy.

Freeware.

I searched the net and everything simple seemed to not have a Secure Certificate for download.

Happy to ignore the above if the source is safe?

Oh, Windows MovieMaker used to have some weird file definition which you had to convert to a .mp4/.avi etc
to be played on regular devices.

Able to be run on Win 10 please.

Thanks in Advance