The order of your slides isn’t set in stone; you can easily rearrange them in the Thumbnails pane.
Click a slide and drag it to a new position.
A horizontal line appears as you drag the slide, indicating where the slide will be moved. When you release the mouse button, the slide is dropped in the new location and all slides in the presentation are renumbered accordingly.
If you need to reorder many slides, it’s easier to use the Slide Sorter view.
If you don’t want a slide to be included in the final slide show, you can hide it from your audience. It won't show up when you play the slide show, but you will still see it in the editing views so you can bring it back in the future.