We need to write 3⁴×4⁵×5⁶ in the form a×10ⁿ where a is not a multiple of 10.

3⁴×4⁵×5⁶=3⁴×2¹⁰×5⁶=3⁴×2⁴×2⁶ ×5⁶=3⁴×2⁴×10⁶.

Hence the number ends in six zeros.