What is the base 8 representation of 30

When converting from base 10 to another base, we first divide by that base

30 / 8 = 3 remainder of 6 (which becomes the rightmost base 8 digit).

we then get the 3 which is smaller than the base and so 3 becomes the final leftmost digit.

(base 10) 30 = (base 8) 36