I cannot convert to mp3 anymore! help - i know i have a really old version of garageband, from 2012.

I have not updated my version of garageband since I got this laptop in 2012 - and now I cannot convert my song to mp3 - it will save, but then not be able to convert to mp3, it just gives the "converting" signal for ever until I turn off my computer and reboot. I have gone in to update garageband, but I get an error message.

Please help.

Thanks, Rose