Bring a large pot of lightly salted water to a boil. Cook campanelle in the boiling water, stirring occasionally, until tender yet firm to the bite, about 12 minutes. Drain and rinse with cold water.
Heat olive oil in a large skillet over medium heat until sizzling. Add garlic; cook and stir until fragrant, 30 seconds to 1 minute. Add salmon; cook until browned and flaking apart, about 5 minutes per side.
Transfer salmon fillets to a bowl with pan drippings. Pour frozen peas on top; let thaw as salmon cools, about 10 minutes. Add campanelle pasta, sugar snap peas, green onions, mustard, lemon juice, and dill; toss gently. Season with salt and pepper.
