What is the way to find the image (filename and where it is) an item has?

I want to edit that image, but I don't know how to locate it.

I can't find anything in the database either. So how does an item is linked with an image?

Hello and sorry for the late reply,

The image is not stored in the database.
Anywhere the K2 item is pulled up, JFile::exists is used (which is used to check if a file exists in the path set) with the path

URL-ROOT."media/k2/items/cache/".md5("image" . K2 ITEM ID HERE)."_XL.jpg" with XL being the site.

$item->image can also be used to display the image's URL.