Unfortunately, you can't directly embed Matterport 3D Showcase into a Microsoft Powerpoint or Google Slides presentation.
However, you can just copy the link and add it to your presentation.
If you're the one giving the presentation and you're not sure about your internet access, then it's best to open the Space beforehand when you practice. Then when actually give the presentation, just switch to the window with 3D Showcase open.
Practice practice practice!
But don't worry. Everyone has technical issues when giving presentations :)