Saks is a famous shop, not a thing you can count like bags. Its full name is Saks Fifth Avenue. It is a big, rather grand department store in New York, known especially for clothes — the kind of place with dressed windows and expensive things inside. People often just say Saks. Fifth Avenue is a well-known street there, so the full name tells you which shop and where. You will see it in films, fashion news, and travel talk. It is a proper name, so it takes a capital letter.

薩克斯第五大道（紐約精品百貨）