From Writing Units ↗:
Exponentiation is indicated by the circumflex accent (^, UTF-8 ^ or ASCII code 94 (alt+94)). For example, input 4.7 m2 as 4.7 m^2
Parentheses are required when there is a risk of misinterpretation. For example, do not input 8 kN m^-2 but rather 8 kN m^(-2).