Preheat your oven to 375°F.
Cook the jumbo pasta shells in a large pot of boiling salted water for 9 minutes until al dente, then drain and set aside.
In a non-stick skillet over medium-high heat, brown the ground turkey until it is fully cooked and no longer pink.
Stir the marinara sauce into the skillet with the turkey and let it simmer on low heat for 5 minutes.
In a medium mixing bowl, combine the ricotta cheese, chopped fresh spinach, garlic powder, dried oregano, sea salt, and black pepper.
Spread half of the turkey marinara sauce into the bottom of a small oven-safe baking dish.
Stuff each cooked pasta shell generously with the spinach and ricotta mixture and arrange them in the baking dish.
Spoon the remaining turkey marinara sauce over the shells and sprinkle evenly with shredded mozzarella and parmesan cheese.
Bake for 20 minutes until the cheese is melted and the sauce is bubbling around the edges.