Download original video as an mp4

We have a user who has made a screen recording in Stream (on SharePoint). He then downloads in order to pull into a video editing program to make further edits (since that capability is not currently available in Stream on SP). It is a .webm file. The Microsoft Video editor doesn't allow this file format to be added to a project. User also could not import into Adobe Premiere Pro. Tried renaming the file to use .mp4 format. Can add into the Video editor but once within the program, the file doesn't work. **Ideally the Microsoft Video Editor would be able to handle the .webm file which was generated from SharePoint**. Any other options other than a 3rd party software tool to convert to another format?????