Make sure to have the base64 to image plugin installed inside your bubble app. There is only one action, called base64 to png which converts base64 text to image.
In order to use this action, make sure you have some base64 text to access, whether it is via another API, a file that is already saved or text inside an element.
After that, create a workflow to be able to input the base64 to png action. Input the base64 text in the base64String text parameter as well as the website_home_url parameter which should be your website home url, it should look something like: https://[id_of_your_app].bubbleapps.io/version-[appVersion]/. Make sure to fill the privacy of the file, name and type of image you want to convert the base64 text to.
After that make sure to retrieve the image in the image_url returned value and save it in a convenient place.

Here is a demo editor using the base64 to png action: https://bubble.io/page?id=base64-to-image-demo&test_plugin=1762114358698x673396622650769400_current&tab=Design&name=index&type=page&elements=bTHDf