The curatorial code of ethics stipulates that curators may not perform appraisals for private individuals or institutions. The Musée du Louvre is therefore unable to carry out appraisals.
However, you may address your query to accredited appraisers such as the Syndicat Français des Experts Professionnels, Drouot Estimations or the Chambre Nationale des Experts Spécialisés.