In Blender you can [Tab] into your mesh, and select the vertices of a campfire if your campfire is a single mesh you can press [Ctrl+L] after selecting a single vertex to get the linked vertices.
Once you have all the vertices you can press [Space] then search for "snap cursor to selection".
If you [Tab] out of your mesh and create a new object lets say a "Cube", and name it "campfire" now you can press [Shift+S] and chose object to cursor, "repeating this process for each campfire".
I don't know if the SDK can import Empties but if it can that might be the better option insted of Cube.
When your done doing that you could just save your blender file, and convert it to j3o in the SDK. Then find your campfire cubes in the Scene Composer, and delete there geometry but leave there nodes.
Finally in your code all you would need to do is:
Node forestScene = (Node) assetManager.loadModel("Scenes/forest.j3o");
Vector3f campfireLocation = forestScene.getChild("campfire").getWorldTranslation();
Vector3f campfireLocation = forestScene.getChild("campfire").getLocalTranslation();
this would work great expecially if you are going to attach a particle emitter then all you would need to do is:
I would probably suggest a hierarchy like the following for you campfire nodes:
+- campfires(Node) +
| + campfire.0(Node)
| + campfire.1(Node)
| + campfire.2(Node)
| + campfire.3(Node)
Witch would allow you to make one control to handle all the campfires.
In case you haven't looked here Blender Key Mapping