How to Trim After a Certain Word using Postmeta

I am trying to syndicated my pod cast to wordpress from blogtalk radio and it keeps sending over code with the files and text. I am able to display a link in the file using get meta

ID, ‘enclosure’, true); ?>”>Play Audio File

But the link looks like this when you click on it

https://www.blogtalkradio.com/diva-toolbox-radio/2010/01/25/janet-powers-interviews-author-gabrielle-bernstein.mp37069698audio/mpeg

and needs to look like this

[audio src="https://www.blogtalkradio.com/diva-toolbox-radio/2010/01/25/janet-powers-interviews-author-gabrielle-bernstein.mp3" /]

I want to trim the output to just chop everything after the word .mp3 because the text before will always be changing and after .mp3 as well.

Should be easy but no luck figuring it out….