You can only use 1 ""Exchange of Night and Day"" effect per turn, and only once that turn. You can activate 1 of these effects.
? Send 1 LIGHT Warrior-Type monster from your hand to the Graveyard, then add 1 DARK Warrior-Type monster from your Deck to your hand, with the same Level the sent monster had in your hand.
? Send 1 DARK Warrior-Type monster from your hand to the Graveyard, then add 1 LIGHT Warrior-Type monster from your Deck to your hand, with the same Level the sent monster had in your hand.