Read 1 Samuel 6:10 Using Other Translations
And the men did so; and took two milch kine, and tied them to the cart, and shut up their calves at home:
The men did so, and took two milk cows and yoked them to the cart and shut up their calves at home.
So these instructions were carried out. Two cows were hitched to the cart, and their newborn calves were shut up in a pen.