This problem description would benefit from an example of the kind of input that could be expected (as well as the correct output).

Based on the description, I thought that I had to replace the string 'o'clock' with the string 'o''clock' (so making it usable in MATLAB.). And no, I did not manage to create input like that.

Instead, you want to replace every single quote with a double quote EXCEPT for the start-and-end quotes.
So 'o''clock' ==> 'o''''clock'

an example would make it clearer

I am not getting it .... Its always showing wrong