"Raj does not have to drink milk."
Translation:राज को दूध नहीं पीना।
We usually use the verb-infinitive+है construction to say 'has to'/'have to'. When doing so, the subject comes with the postposition को.
राज को पीना है - 'Raj has to drink'.
राज को दूध पीना है - 'Raj has to drink milk'.
राज को दूध नहीं पीना - 'Raj doesn't have to drink milk' where we've dropped the है because it is optional in negative sentences.