If you have created slides in the past that you wish to reuse in your current presentation, you can import the slides you require, or simply copy and paste them from the original presentation into your new presentation. When importing or copying the slides, you will be able to decide whether to keep the formatting the same as in the original presentation, or to match the formatting in the new presentation.
You can import slides easily from one presentation to another as follows:
Click on the File menu, then choose Import Slides
Choose the presentation you wish to import slides from, then click on Select
Choose the slides you wish to import
Choose to keep original theme if you want the slides to be inserted as they look in the presentation you are importing them from
Click on Import slides
If you copy a slide from one presentation to another, you will be asked if you want the slide to stay formatted in the same way as the source presentation, or to match the format of the target presentation.
To copy slides between presentations:
In the navigation pane on the left-hand side of the screen, click on the slide you wish to copy, then press Ctrl C to copy it. Alternatively, you can right-click over the slide and choose Copy.
the target presentation, click on the slide you wish the inserted slide to appear after
Press Ctrl V to paste the slide
Choose whether you wish to link data to the original presentation or not. If you choose to Link & keep original styles, the slide in the target presentation will update automatically whenever the content of the source slide is changed.