66 The outstretched arm is a bold anthropomorphism. It describes the power of God. The Egyptians will later admit that the plagues were by the hand of God (Exod 8:19).
67 The word נִפְלְאֹתַי (niflé’otay) does not specify what the intervention will be. As the text unfolds it will be clear that the plagues are intended. Signs and portents could refer to things people might do, but “wonders” only God could do. The root refers to that which is extraordinary, surpassing, amazing, difficult to comprehend. See Isa 9:6; Gen 18:14; Ps 139:6.
68 The two uses of the root שָׁלָח (shalakh) in this verse contribute to its force. When the Lord “sends” (Qal) his hand, Pharaoh will “send” (Piel) the Israelites out of Egypt.

In other versions

So I will stretch out my hand and strike Egypt with all the wonders that I will do in it; after that he will let you go.

So I will stretch out my hand and strike the Egyptians with all the wonders that I will perform among them. After that, he will let you go.

But when I stretch out my hand and strike Egypt with all my miracles that I will perform in it, after that, he will let you go.

So I will raise my hand and strike the Egyptians, performing all kinds of miracles among them. Then at last he will let you go.

And I will stretch out my hand, and I will strike Egypt with all of my wonders that I will do in its midst, and afterward he will release you.

And I will stretch out my hand, and smite Egypt with all my wonders which I will do in the midst thereof: and after that he will let you go.

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