How can you get lost isbn numbers of the books?

To find lost ISBN numbers of books, you can start by checking online databases such as WorldCat or google Books, which often provide ISBN information for a wide range of titles. Additionally, you can look up the book on the publisher's website or consult library catalogs. If you have a physical copy, the ISBN is typically found on the back cover or inside the copyright page. Lastly, book retailers like Amazon may also list the ISBN in their product details.