Let p be a prime number. Find all roots of x^(p-1) in Z_p

I have this definition.

Let f(x) be in F[x]. An element c in F is said to be a root of multiplicity m>=1 of f(x) if (x-c)^m|f(x), but (x-c)^(m+1) does not divide f(x).

I'm not sure if I use this idea somehow or not.