BUPA is a private medical insurance scheme...nothing to do with NI.
You and your daughter are also entitled to NHS (National Health Service).
If you are permitted to work, then you need to apply for a NI number from your local jobcentre.
National insurance is concerned with benefits from, and contributions towards the government-run benefit (incl pensions) scheme from your employment or self-employment.
If registered unemployed or in jail, the govt pay the contributions for you.