You do need to know if n1 is bigger or smaller than n3.
You cannot make any calculations unless you know the numerical value of n3.
You cannot make any calculations unless you know the numerical value of n2.
The reflected ray from the interface between medium 1 and medium 2 will undergo a different phase change than the ray reflected from the interface between 2 and 3.
You cannot make any calculations unless you know the numerical value of the thickness of layer 2.
You cannot make any calculations unless you know the numerical value of n1.