Zamzar is an easy- to-use program for you to export MP3 files from any video formats. It can also send the changed file to an email address directly after conversion. But the free version of Zamzar is slow and the maximum size of your file is 50MB.

Step 1.Add Files that you want to convert.

Step 2.Choose the audio format MP3 in the Convert To drop-down list.

Step 3.Click the Convert Now button to get your MP3 file.

Reading more: https://www.free-videoconverter.net/mp3-converting/wmv-to-mp3/