Convert Blob to wav file in js to send it in the body of a POST request

I’m working on a project where I need to send an audio file through a form-data body in a POST request.
But the audio file comes from the browser, recording my microphone and giving me a blob of the record.
I need to convert this blob to a wav/mp3 file and send it to my request.
Here is the blob I get :
raw code of the blob
So, how can I properly convert it to an audio file and send it in a form-data body in my fetch function ?
Thanks a lot !

I tried to parse the blob, to stringify it, but nothing worked for me.