how to find isbn number of old book that has no barcode
Book that were printed pre-barcode days can usually be found on the verso of the title page - that is the backside of the title page. Make sure you are looking at the full title page, which will normally include the author and publication information (half-title pages are usually just the title and occur earlier in the book). On the verso you will often find publication information and since the 1960s you are likely to find a catalog record which contains all the information you need. If there is no CIP data you often will at least see the date of publication and an ISBN. Before 2008 all ISBNs were only 10 digits long.
Occasionally publication information may also be found at the end of a book although that is rare except in the case of some "easy" children's books. But not impossible that the information could be there.
If the book is older than the 1950s you may or may not find any kind of ISBN as prior to that time it was not a systematic addition to a book or wasn't available at all. Books that were self-published often do not have ISBNs either.
Sometimes ISBNs were added after publication if the book was still in print, but you can only find that information in a cataloging record or publication catalog. You can always search WorldCat to see if your edition has had one added to the cataloging record.