Translation:I want three liters of cow milk, please.
one talks about cows milk, goats milk, sheep (because it is the same for singular and plural) milk etc in English as far as I am aware. Perhaps you could argue it should be cow's milk etc
In the southern USA, it is quite common to say "cow milk" ( possibly following the same rule as "Christmas tree" with respect to nouns being used as adjectives). :)
I would like is much more common than I wish for, it should be accepted as an answer.
I disagreethat it should be accepted.
"I would like" is used for politeness and is heard more often, but it would require the Conditional Tense "Aș vrea".
"I want" is more direct, and a better tx of "Vreau" per the question.
Agreed on "I want" but "I wish for" is also accepted. Which I have never heard anyone tell a cashier, ever.