Cubik Studio

I created a weapon model, I begin to export, pops up a window with the inscription: "Your model uses 3 unsaved textures. To proceed, Cubik Studio exported them as PNGs beside JSON. Move all PNGs if necessary."
I did not pay attention to it, and saved. I enter the game, I have a black and purple weapon, but one texture is loaded.
I don't understand exactly where to throw PNGs into a resource pack. They say that in JSON you need to write the paths to PNG files, and I do not understand this, since I am Russian.

You have to choose the right Folder ...

...if you have choose that your 3d model is a item then you have to save all of the textures in the items Folder which you have to create.
...if you have choose that your 3d model is a block then you have to save all of the textures in the blocks Folder which you have to create.