Since you asked for an accurate translation, be careful with the word billion:
American English a billion = 1,000,000,000. (also true in Brazil, France, and other contries)
British English a billion = 1,000,000,000,000 (also true in UK, Portugal, Spain, Germain, and other countries).
A billion (nine zeros) in American English = a thousand million in English British
So, if you are translating a billion in American English to European Portuguese it is a thousand million (mil milhões).
-Put the word or phrase in the title when asking a question.
(Avoid "translation please", "how do I say this", "does this word exist", "I'm new" and similar expressions.) - Provide an example sentence to show the context, whenever possible. Additional comments on the application for technical terms are strongly suggested.