ambrosia salad recipe

1 cup sour cream or Greek yogurt 1 cup whipped topping (like Cool Whip) 1/2 cup sweetened shredded coconut 1 cup mini marshmallows 1 can (11 oz) mandarin oranges, drained 1 can (20 oz) pineapple tidbits, drained 1 cup maraschino cherries, drained and halved 1/2 cup chopped nuts (optional) 1/4 cup powdered sugar (optional, for added sweetness)