Sounds like there are one or more other issues here. ScreenRecorder4 only records
.MP4 videos, and each is given a long numeric name based on the year, month, day and time you started the recording, such as
20211109104049.mp4.
If you've selected the option to also record mouse clicks, there will be a corresponding file named
20211109104049_mp4.mrk. That file contains no video and can only be read by PD and the SR4 app. It's automatically loaded whenever a matching MP4 video is added to the media library and will add expanding colored circles on the screen at each mouse click in the recorded stream.
If you truly have
.mkv/.mvk files they must have come from a different screen recorder. You can get more info on them by dragging one of them onto the MediaInfo Online browser
page.