How to use "Extract with Regrex" to pick up value from JSON

Need help APIs
1

Hi, I have a JSON data, but I want to extract only one value from this text.
I still haven’t quite figured out how to use it “extract with regrex”.

Can you help me?

This is a JSON data:

image
image692×132 21.9 KB

I want only want to extract:
QmaYDjSxjefTzG5BFPF12FM6CK4AjaxBh3WDTnx58CGusE/5799.png

Thanks!!!