help converting dvd with close captions to mp4 with hard subtitles

[kasfig]

Dear friends
Please can anyone help with the above problem.
I have in my possession a DVD disk which I watch on the television - it runs from the normal standalone DVD player .
This DVD disk has a menu: there are three documentary movies (videos) and one can choose from the menu which to watch (in the usual way of course).
The three movies make up a series of three: originally these were three VHS videotapes which came out in the 1980's and later the producer decided to make this series all on one DVD.
The original tapes had close-captioned subtitles, which could be viewed on the tv screen
On the DVD version the subtitling remains the same - it is the close captioned variety.
What I would like to do if possible please is to produce three MP4 files: one for each film. Furthermore, I would like to preserve the subtitles in the MP4 files that result. These to be hard coded (permanent).
I am just a layperson. I have little or no expertise in this area apart from being a novice having tried out a few things.
Please can anyone advise whether it would be possible to do the conversion job described?
Best wishes
Ian