How do I modify the self illum diffuse shader to not cull backfaces?

I'm really new to this an I'm trying to modify the self illumin shader so that it doesn't cull the backfaces of my geometry. Here is the code I tried modifying:

 Shader "Self-Illumin/DiffuseBackface" {
 Properties {
     _Color ("Main Color", Color) = (1,1,1,1)
     _MainTex ("Base (RGB) Gloss (A)", 2D) = "white" {}
     _Illum ("Illumin (A)", 2D) = "white" {}
     _EmissionLM ("Emission (Lightmapper)", Float) = 0
 }
 SubShader {
 
     Tags { "RenderType"="Opaque" }
     LOD 200
     
 CGPROGRAM
 #pragma surface surf Lambert
 
 sampler2D _MainTex;
 sampler2D _Illum;
 fixed4 _Color;
 
 struct Input {
     float2 uv_MainTex;
     float2 uv_Illum;
 };
 
 void surf (Input IN, inout SurfaceOutput o) {
     fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
     fixed4 c = tex * _Color;
     o.Albedo = c.rgb;
     o.Emission = c.rgb * tex2D(_Illum, IN.uv_Illum).a;
     o.Alpha = c.a;
 }
 ENDCG
         Pass {
             Cull Off
         }
 } 
 FallBack "Self-Illumin/VertexLit"
 }

Notice I added the Pass{Cull Off} I don't think that's right..