Using FFMPEG how do I convert an entire folder of webm files to wav or mp3?

[alphainventions]

What is the script for converting an entire folder of webm and mp4 files to mp3 or wav into a new folder using ffmpeg on windows.

I also need instructions on how to run the script on windows.

[hello_hello]

I do that sort of thing using AnotherGUI. It's a tiny download and doesn't need to be installed. Just unzip it somewhere and run it. Tell AnotherGUI where to find ffmpeg, click "Edit" to create a preset and copy and paste the following into the "first pass" section:

-i "<FullSourceFileName>" -y -threads 1 -vn -acodec pcm_s16le "<OutputPath><OutputFileName>.wav"

Give the preset a name and save it. Make sure it's selected and drag and drop your folder of files onto AnotherGUI. Use Ctrl+A to highlight them all and click "change output path" to select the output location. Click "Go". That should get ffmpeg to ignore any video and convert the audio to 16 bit wave files.

Converting to MP3 would look like this:

-i "<FullSourceFileName>" -y -threads 1 -vn -acodec mp3 -ab 128 "<OutputPath><OutputFileName>.mp3"

By default AnotherGUI runs processes in multiple threads. You might want to reduce the number it'll run simultaneously or change it to "1" under Preferences for hard drive intensive jobs, so they only convert one at a time. If the jobs result in an error for some reason, add -report to the command line and try again:

-report -i "<FullSourceFileName>" -y -threads 1 -vn -acodec mp3 -ab 128 "<OutputPath><OutputFileName>.mp3"

That'll get ffmpeg to save a detailed log which usually indicates what the problem is. If it doesn't appear in the output folder, have a look in the folder where AnotherGUI is located.
If you need to down-mix the audio to stereo someone else might need to help you with that. I'd have to check the command line options as I don't use ffmpeg for that myself.