This is a good, grammatical, natural-sounding English sentence, if that's your question.
By the way...
You can say either "What are" or "What were." Both are correct. "What were" is correct because you saw the exhibits in the past, and they impressed you in the past. Assuming permanent exhibits, "what are" is also correct, because the exhibits still exist and still can be seen.
If someone just wanted the story of my visit, they might ask "What were the three things that impressed you the most..." If someone was planning to visit the museum and wanted advice on what to see, they might ask "What are the three things that impressed you the most..."