Do you have an answer, if I got the same I'll post the solution.
Divide (root3 - i)^m to both sides as it can't equal 0.
Change both numerator and denominator to mod arg form.
(2cispi/6)/(2cis(-pi/6)) = 1
(cispi/3)^m = cis0 (De Moivres)
mpi/3 = 0 + 2kpi (k is an integer)
m = 6k and the smallest positive m is when k = 1, therefore
m = 6