Flip -Flop is a binary cell capable of storing 1-bit of information. so to store n-bit we need n Fli-Flip.
n-bit Ring Counter can have n different output states.
n-bit Twisted ring counter(Johnson Ring Counter) can have 2n different output states.
n-bit ripple counter (mod-2n counter) can have 2n different output states.
so i mean to say
A Ring Counter that consist n Flip-Flip will have n-states.
3-bit ripple counter is called as MOD-8 counter. So in general, an n-bit ripple counter is called as modulo-N counter. Where, MOD number = 2n.
so MOD-258 counter needs 9 bit to store all states so ultimately 9 Flip-Flop.
Tell me if i went wrong somewhere.