Batch conversion of a folder of .WEBM to .MP4 files?

[guntherfriend]

Hi, I would like help learning how to do a batch conversion of a folder of .WEBM to .MP4 files? In the player, after I click on convert, it appears I can add several files to the file selection box. But I can see no option for designating simply a folder or other for a destination. I was able to read instruction at the VLA Wikipedia site about making a .BAT file. I tried to follow them but don't have a clue about how such files are supposed to work. So I would appreciate advice on how to proceed. Doing one file at a time is tedious.