The length of each curtain is to be forty-two feet, and the width of each curtain is to be six feet -- the same size for each of the curtains.

The length of one curtain was forty-two feet, and the width of one curtain was six feet -- the same size for each of the curtains.

and you are to make forty silver bases to go under the twenty frames -- two bases under the first frame for its two projections, and likewise two bases under the next frame for its two projections;

He made forty silver bases under the twenty frames -- two bases under the first frame for its two projections, and likewise two bases under the next frame for its two projections,

and their forty silver bases, two bases under the first frame, and two bases under the next frame.

and their forty silver bases, two bases under the first frame and two bases under the next frame.