An mp4 is a video file type, but the .mp4 in the file name is the file extension. Usually, these things should match, but ...

Now type the following in it and hit Enter: ren *.* *.jpg Here we are using a wildcard as we want any file extension to be changed to jpg. When you do this, you will see that all the files in the ...

This will show you all of the file names of all the files in that location. Type ren "FILENAME.OLD-EXTENSION" "FILENAME.NEW- EXTENSION" with the filename as the name of the file and the old extension ...