Problems with Pics from .png to .jpg

Hi, the last week I was runnig the WP smush pro plugin with and put on the option to convert the pics on .png to .jpg.
Then that pics change the name and extension. Now, I have a lot of products without pics, because not found the new pic with the new extension. I'm talking about more than 10.000 pics.
How can I fix that problem?
Thanks.

Raúl Sierra.