When raising an exponential expression to another power, you multiply the exponents.
Formula: $(a^m)^n = a^{m \times n}$
Examples:
$(5^3)^2 = 5^{3 \times 2} = 5^6$
$(7^5)^2 = 7^{5 \times 2} = 7^{10}$
$(6^k)^5 = 6^{k \times 5} = 6^{5k}$