Screen Recording w/No Sound - Can I recover the audio?

Hello!

So I just realized that screen recording on my MacBook Pro (Catalina) doesn't record the sound like it does on my phone. I downloaded a configuration to QuickTime that now allows me to record sound for future screen recordings, but I have one video that was recorded before I realized this and it has no sound.

Is there any way to recover the sound on the soundless video or is it a lost cause? Really trying to save it and get the sound if possible.

Thank you!