Short answer: There are many people with the surname Trump, but if you’re asking about Donald Trump himself, there is one primary individual who is widely known as “Donald Trump.” He has several immediate family members and descendants, but the phrase “how many Donald Trumps are there” usually refers to how many people share the name “Donald Trump.” The surname is shared by thousands of individuals in the United States and elsewhere, but a single, well-known public figure is Donald J. Trump. If you meant something else by your question (for example, how many people named Donald Trump exist in a certain dataset, or how many people in his family share the name Donald), please specify the context and I can tailor the answer.