Maybe you weren't paying attention to the screen prompts?
Maybe you do not have a converter with the capabilities you think you do?
Maybe you did not select the right item within the PDF file to convert?
Maybe you did not define a proper output location?
Maybe you did not go to the proper output location?
How the heck are we supposed to know what you did wrong?
We don't even know what you were using for a converter, if it is a converter.
Maybe, maybe, maybe.
I'd like to help you, but you first gotta help me help you.
Perhaps you don't even need to use any converter at all, if all you need to capture part of a graphic from what is on the screen. That's another maybe.
I used the converter to turn a pdf into jpg file. But the Output is "empty"! What did I do wrong??