Carlos had 56 pencils.

To find out how many boxes Carlos needed, you can divide the total number of pencils by the number of pencils per box.

Carlos had 56 pencils and each box can hold 8 pencils.

So, the calculation is:

\[ \text{Number of boxes} = \frac{\text{Total pencils}}{\text{Pencils per box}} = \frac{56}{8} = 7 \]

Carlos needed 7 boxes to hold all the pencils.