Open your camera app. Scroll all the way down to change the place for storage of your pictures: memory card or phone.
Open any picture and choose settings. Scroll down to tap Details. Last information in that list of details is the path of storage. For instance: /storage/extsdcard/dcim/camera/... which means it's on the memory card, in a folder DCIM, which contains a folder Camera in which this specific picture is stored.
