Click the “Choose Files” button to select your 3GP files. Click the “Convert to MP3” button to start the conversion. When the status change to “Done” click the “Download MP3” button. Part 3: The 5 Best MP4 to MP3 Converter Online for Free. After knowing the mentioned professional ways, you must be wondering how to convert MP4 to MP3 format online for free. And here are the selected 5 best MP4 to MP3 online converters. You can learn about the features, pros, and cons in detail in the following introduction. 1. Convertio Convert.online is an free online service, which allows you to download/convert your favorite videos to mp3, mp4, 3gp, webm. You can convert music from video-hosting sites including YouTube, Vimeo, Dailymotion, Metacafe, Facebook and more. Convert your MP3 to MP4 video format using this tool by Video Candy. No additional software needed. MP3 to MP4 Online and free MP3 to MP4 converter . Add file Here are 2 steps to convert Facebook video to MP3: Step 1. Copy a video URL from Facebook and paste it into the search box of AmoyShare MP3 Converter. Step 2. Click Download and choose an MP3 audio format to convert. Here is a quick tip, AmoyShare MP3 Converter supports to find videos by searching keywords in the search box of MP3 Converter. Online UniConverter supports convert MP4 videos to MP3 audio files easily. Just open this handy free video converter, drag MP4 files to the interface, then choose output format as MP3 from the Audio tab. Finally, click the Convert button and wait for downloading. pTImrj.