I have a dm sword with sharpness 3 and book with sharpness 2 but he stay to sharpness 3 what i need to do to get sharpness v???
You can only combine enchantments with the same level, otherwise it just uses the highest level.
So 2 Sharpness III will combine but only give you Sharpness IV
To get Sharpness V from combining enchantments you'd need 2 Sharpness IV
(or 1 Sharpness IV and 2 Sharpness III combined in 2 steps, or 4 Sharpness III combined in 3 steps.)