Putting cake mix on the label is definitely not sufficient. You need to copy the ingredients from the box to put on your label.
Tennessee is one of the only states that doesn’t seem to require things to be individually packaged. But I do think they’d prefer individual packaging where that’s reasonable or expected. A bulk container situation would be common with baked goods, like bread (donuts, bagels, etc). An example where an item wouldn’t be prepackaged but also wouldn’t be sold in bulk would be cotton candy made on-the-spot.
But, there is nothing in the law that requires items to be individually packaged. The main intent of the law is that the customer is informed. So in cases where items are not packaged and labeled, the label and ingredients need to be on the bulk container or a placard to notify the customer.