Moses continues to speak to the people of Israel as if they were one man, so all instances of "you" and "your" are singular. (See: [[rc://en/ta/man/jit/figs-you]])
Here "a mighty hand" and "an outstretched arm" are metaphors for Yahweh's power. See how you translated these words in [Deuteronomy 4:34](../04/34.md). Alternate translation: "by showing his mighty power" (See: [[rc://en/ta/man/jit/figs-metaphor]])