By PE9, do you mean Premiere Elements 9 or Photoshop Elements 9?
If this is a Photoshop Elements question, it's probably better answered in the Photoshop Elements forum.
If this is about creating a slideshow in Premiere Elements, import the photos in a Premiere Elements project using Get Media/From Files and Folders. In the Premiere Elements Project panel, you can arrange the order of your slides in a number of ways, including alpha-numeric.
And don't forget, if you're planning to use these photos in a video slideshow to resize all of your photos to no larger than 1000x750 pixels before you bring them into your Premiere Elements project!
Premier Elements 9 - the only options I see in the organizer is "newest or oldest first"..I am creating a slide show from 450 slides/photos. they are all number in order, but once I brought them into the organizer, the became scrambled
I did not know about resizing, what purpose or effect will that have?
IN GOD WE TRUST
If you don't resize your photos, the program may work very slowly or choke. In fact, if you try to use photos that are too large, the program will reject them completely.
Trust me. You want to optimize your photo sizes.
Are your photos in your Premiere Elements Project panel (not the Organizer or the Media panel)? If so, clicking on the header for the Title column will arrange your files in alpha-numeric order.