I cannot find my iPhoto library folder in my mac

Barbara,

by default your iPhoto library is in your Pictures folder and called "iPhoto Library.photolibrary" and showing an icon like a fan of pictures.

You may have stored the library somewhere else.

Ctrl-click the word iPhoto in the title bar of the iPhoto main application window. This will show a drop-down list with the path to your iPhoto library. Click the folder you see there to reveal your library.

-- Léonie

so after I do my backup in my external drive, can I delete my photos in iPhoto?

Make sure, your external drive has the correct filesystem and is formatted MacOS Extended (Journaled), Barbara.

See this link: Format external drives to Mac OS Extended before using with Aperture

You can check the formatting by selecting the drive and using the command "File > Get Info".

Once your library is on the external drive, double click it to open it in iPhoto, and test it before you delete the library on your internal drive.

But note, the copy of your external will not be a backup. It will be your main working copy. You need a second copy of the library as a backup on a different drive for safety. Drives do fail, and you will want to have a copy of your photos on different drive, when that happens.

This is not a backup - it is moving your working copy of the iPhoto library to an external drive - you must also have a backup of everything including the library on the external drive on a second external backup drive

LN

You are welcome

LN