New Revised Standard Version
For if you will not let my people go, I will send swarms of flies on you, your officials, and your people, and into your houses; and the houses of the Egyptians shall be filled with swarms of flies; so also the land where they live.

Contemporary English Version
If you don't, he will send swarms of flies to attack you, your officials, and every citizen of your country. Your houses will be full of flies, and the ground will crawl with them.

New American Bible
For if you do not let my people go, I will send swarms of flies upon you and your servants and your people and your houses. The houses of the Egyptians and the very ground on which they stand will be filled with swarms of flies.

Douay-Rheims Bible
But if thou wilt not let them go, behold I will send in upon thee, and upon thy servants, and upon thy houses, all kind of flies: and the houses of the Egyptians shall be filled with flies of divers kinds, and the whole land wherein they shall be.

But if thou wilt not let them go, behold I will send in upon thee, and upon thy servants, and upon thy houses, all kind of flies: and the houses of the Egyptians shall be filled with flies of divers kinds, and the whole land wherein they shall be.

swarms.

Psalm 78:45 He sent amongst them divers sorts of flies, which devoured them: and frogs which destroyed them.

Psalm 105:31 He spoke, and there came divers sorts of flies and sciniphs in all their coasts.

Isaiah 7:18 And it shall come to pass in that day, that the Lord shall hiss for the fly, that is in the uttermost parts of the rivers of Egypt, and for the bee that is in the land of Assyria.