Preheat your oven to 375°F and lightly grease a small baking dish.
Bring a pot of salted water to a boil and cook the jumbo shells for 2 minutes less than the package directions until slightly firm; drain and set aside.
In a large skillet over medium heat, add the olive oil and brown the ground turkey until fully cooked and no longer pink.
Add the fresh baby spinach to the skillet and sauté for 1-2 minutes until just wilted, then remove from heat to cool.
In a medium mixing bowl, combine the cooked turkey and spinach with the ricotta cheese, garlic powder, oregano, sea salt, and black pepper.
Spread half of the marinara sauce across the bottom of the prepared baking dish.
Carefully stuff each cooked pasta shell with a generous amount of the turkey and ricotta mixture and place them in the dish.
Spoon the remaining marinara sauce over the shells and sprinkle evenly with the parmesan cheese.
Cover the dish with foil and bake for 15 minutes, then remove the foil and bake for an additional 5 minutes until the cheese is melted and the sauce is bubbly.