Evidently Exodus 11:1-3 should be viewed as being parenthetical.

Only by knowing that the 10th plague would be the very last could Moses have told Pharaoh that he would not try to see his face again. Otherwise, it would have been presumptuous for him to agree to something that might not have been in harmony with Jehovah’s will. The words of Exodus 11:1-3 reveal that Moses was aware that the 10th plague would be the last, and these words also supply information as to what the Israelites were to do after that plague came upon the Egyptians.​—Compare Exodus 11:2, 3 with Exodus 12:35, 36.