To find the length of the boxes in the new drawing with the scale factor of 1 box = 12 inches, we first calculate the length in inches according to the original scale factor.
Since 1 box = 6 inches, for 10 boxes:
\[ 10 \text{ boxes} \times 6 \text{ inches/box} = 60 \text{ inches} \]
Next, we need to convert this length into the new scale factor of 1 box = 12 inches. To find out how many boxes this length of 60 inches represents at the new scale, we divide the total length by the new box size:
\[ \text{Number of boxes} = \frac{60 \text{ inches}}{12 \text{ inches/box}} = 5 \text{ boxes} \]
Therefore, in the new drawing, the length will be 5 boxes.