If you look up Impressionism by subject or keyword in the catalog you will see that there is no predominant call number where the books are found.
It depends on what you are looking for: for instance, Edouard Manet is ND553.M3, but it will vary by Impressionism in which country, which artist, etc., so it is not so simple.
You'll need to be more specific when you look up terms in the library catalog to get a sense of some call numbers to start browsing in the library book stacks.