How to transfer mp4 files to my iPhone x

Hi: Should be simple but I've tried 3 or 4 different 'methods' from the web and none worked. All I want to do is copy some MP4 video files on my MacBook to my iPhone X and be able to watch them on the iPhone. Ideally I would like to be able to copy a few folders of MP4 files but even if I can only copy the videos without their folders, that would be acceptable. I find all these suggestions about using iTunes (which no longer exists!) and methods of dragging the files in MacBook Finder App and dropping them on the iPhone device in the left column of Finder and that doesn't work either. I try to use sync but none of the files in my MacBook MOVIES folder show up as available to sync to iPhone. Please help. Thanks.

Peace and blessings,

Donn