Open the YouTube video you want to convert
Copy the video URL from the address bar
Go to a YouTube-to-MP3 converter website or app
Paste the copied URL into the converter
Select MP3 as the output format
Choose the audio quality if available
Click the convert or start button
Wait for the conversion to finish
Download the MP3 file to your device
Save the file in your preferred folder
Make sure you have the right to download and convert the content