If the main point of your work today is to learn all about all factors, they may want you to think of other numbers that multiply to 42, such as 1×42 and 2×21.
That would look like 1 row of 42 blocks and 2 rows of 21 blocks.
OR OR OR
If the main idea is learning that 3×14 is the same as 14×3 and 6×7 is the same as 7×6, then the answer might actually be 14 rows of 3 blocks and 7 rows of 6 blocks.