There is no such built-in function in func, which is why you have to implement it yourself. I would advise using binary exponentiation, because this solution can save gas for you

;; Unoptimized variant
int pow (int a, int n) {
    int i = 0;
    int value = a;
    while (i < n - 1) {
        a *= value;
        i += 1;
    }
    return a;
}

;; Optimized variant
(int) binpow (int n, int e) {
    if (e == 0) {
        return 1;
    }
    if (e == 1) {
        return n;
    }
    int p = binpow(n, e / 2);
    p *= p;
    if ((e % 2) == 1) {
        p *= n;
    }
    return p;
}

() main () {
    int num = binpow(2, 3);
    ~dump(num); ;; 8
}