To add to Paul's reply,

While you could say "miss" to address a younger woman you don't know, you might say "ma'am" for a woman who is older.  There is no clear line on when you would call someone "ma'am" instead of "miss".  I guess it depends on the age of the speaker and the age of the woman.  It can be a joke in the US that, as a woman, you know you are getting older when people start calling you "ma'am".  For example, my wife might come and say, "God, I'm getting old.  I was at the grocery store and every young kid working at the cash registers kept calling me ma'am".

Also, a suggestion: when writing, use the word "and" instead of "n" and use "you" instead of "u".  Often when speaking "and" sounds like "n", but when writing you should write "and".