I want to make my powerpoints into videos for online teaching
For Powerpoint search on a Powerpoint forum.
To transform a presentation into a video you could use this extension: Impress video converter | Apache OpenOffice Extensions
But this extension only seems to work for OpenOffice. It’s easy to install OpenOffice (also as a portable version) and to test the above mentioned extension.
If the extension does not work for your purposes: Check a screencast app which can do. Recommended: simplescreenrecorder (Linux only).
Screen Recorder Lite for Windows.
Has not been tested by me.