The few addresses that I heard in the movie 'The Help' were not particular to 'the help'.
- 'miss' (for an unmarried female)
- 'ma'am' (for a married female)
- 'sir' (for an adult male).
For young males, I'm not sure (I have a hard time believing an adult black would feel compelled to say sir to a 10-year old boy, at least in the 60's), but there were no young males in the movie to address.
During that time period, if these were not used it would be a sign of disrespect.
These would be used between any race (whites to whites, whites to blacks) but from whites to blacks there might be an age shift (because of racial disrespect (e.g. for a white person the threshold to start calling a black person 'sir' might be much older).
Though these forms are pretty much the same in AAVE and in Southern American English (these two share many features separate from GenAmE), in speech, they might be elided differently and this is what may be heard in the movie. "No'm", "Yes'm" might be what you heard.
If you include the name of the person you are addressing, you'd say (respectively)
- Miss Ellen (Miss + first name) if familiar or Miss + last name if not familiar)
- Missus Jones
- Mister Jones
For whites in the South it is not uncommon to still hear miss/ma'am/sir, mostly in commercial or business situations; that is, it is slowly dying off, whereas in the rest of the country is has been long gone. For blacks and interracially, I'm not sure.