This is the 13818th most frequent Russian word.
нужна
"Нужна" means "needed" or "necessary" (feminine form).
Here, 'нужна' agrees in gender and number with 'книга' (feminine singular).
Мне нужна книга.
I need a book.
In this example, 'нужна' matches the gender and context of 'организация' (feminine singular).
Для работы нужна хорошая организация.
For work, good organization is needed.
The word 'нужна' is used because 'помощь' (help) is feminine singular, and 'ему' indicates the person in need.