You can get back your PPT files if you enabled the cloud storage before. If not, you are suggested to utilize iBoysoft Data Recovery for Mac, an effective and professional software to recover data.
- Recover with iCloud. Open iCloud.com in your browser, and type your Apple account and password. Then click Account Settings, find Restore files, select your wanted PPT files, and click Restore.
- Recover with Time Machine. (you set an external drive for Time Machine backup.) Finder > Applications > Utilities > Time Machine > Look through the timeline and select your wanted files > Select Restore.
- Recover with iBoysoft Data Recovery for Mac. (if you do not have any cloud storage.) Free download, install and open it, then select the drive you stored your PPT files, click Search for Lost Data, then preview and choose your wanted PPT file after scanning, click Recover to save them to another place.
Hope you can find your PPT files.
Also read: How to Recover Overwritten Files on Mac.