First of all, what you should do in every problem of this type, is to choose an appropriate set of axis and draw the Free Body Force diagram.
In the inclined plane questions, it is easier to solve a problem if you choose the co-ordinate axis (ie, x&y axis) as along the plane and perpendicular to the plane.
Next, identify all the forces acting on the block and find the components of each force along the axis.
Since the body is not accelerating, what is the sum of the forces acting along the plane? Can you find the value of friction from this?