"Maps of cities"
is it not a map this mapy but a plany thing
also confused as to whether mapy is singular or plural for they have "nie mam mapy" singular
you have a very nice explanation in a comment below, but to fully understand it you have to read more about grammatical cases in Polish - this is the thing that causes a LOT of commotion, as many forms repeat in different cases, whether plural or singular. Unfortunately, to understand Polish grammatical cases, if you are not a native speaker, you will need much time, many examples and some good literature :) Also, 'plan miasta' would be 'a city plan', but in Polish it is possible to use 'plan miasta' [a city plan] and 'mapa miasta [a city map/a map of the city] interchangeably.
mapa (one) = singular mapy (two) = plural
Nie mam (1) mapy = singular Nie mam (2) map = plural Applies to negation
Mam (1) mapę = singular Mam (2) mapy = plural Applies to confirm ;-)