Looks like that pack already has a .object, you shouldn't need to export any of the objects manually unless you're making edits to them. You can find it here :
https://drive.google.com/drive/folders/161H_ElvI9dxYQAYHLNIqA2enCcNPjtZV, just put HalloweenSpooks.object in your objects folder (FeralHeart\media\objects), and make sure everything from the my_objects .zip goes in FeralHeart\media\objects\my_objects. It should look something this, make sure they aren't in another folder.