Great example for a famous philosophical thought experiment called ship of theseus. It actually happens like every seven years that all body cells get fully replaced, but i would say that the "you" is memory stored in your brain, behaviour, emotions, etc
That’s an interesting question, but as others have already mentioned above, it’s the Ship of Theseus paradox; well, that’s the philosophical part. From a biological standpoint, what actually happens is an internal renewal; in other words, it’s not a replacement with parts from another source, but rather an internal renewal, they are copies of your own DNA, and the foundation of your memory, personality, and identity remains the same from birth to death; therefore, we are the same person.