converting standard customer shaders to work in HDRP

hi all, i've just imported everything i need to get the VFX graph working in unity but forgot i had a custom shader on my terrain, i've had a look around and it seems nearly impossible to convert them easily, how can i recreate this shader on the HDRP, i am very inexperienced when it comes to shader code and i've only just installed the shader graph so have yet to play around.

Code (CSharp):

1. Shader "Custom/Terrain" {
2.     Properties {
3.         testTexture("Texture", 2D) = "white"{}
4.         testScale("Scale", Float) = 1
5.  
6.     }
7.     SubShader {
8.         Tags { "RenderType"="Opaque" }
9.         LOD 200
10.        
11.         CGPROGRAM
12.         // Physically based Standard lighting model, and enable shadows on all light types
13.         #pragma surface surf Standard fullforwardshadows
14.  
15.         // Use shader model 3.0 target, to get nicer looking lighting
16.         #pragma target 3.0
17.  
18.         const static int maxLayerCount = 8;
19.         const static float epsilon = 1E-4;
20.  
21.         int layerCount;
22.         float3 baseColours[maxLayerCount];
23.         float baseStartHeights[maxLayerCount];
24.         float baseBlends[maxLayerCount];
25.         float baseColourStrength[maxLayerCount];
26.         float baseTextureScales[maxLayerCount];
27.  
28.         float minHeight;
29.         float maxHeight;
30.  
31.         sampler2D testTexture;
32.         float testScale;
33.  
34.         UNITY_DECLARE_TEX2DARRAY(baseTextures);
35.  
36.         struct Input {
37.             float3 worldPos;
38.             float3 worldNormal;
39.         };
40.  
41.         float inverseLerp(float a, float b, float value) {
42.             return saturate((value-a)/(b-a));
43.         }
44.  
45.         float3 triplanar(float3 worldPos, float scale, float3 blendAxes, int textureIndex) {
46.             float3 scaledWorldPos = worldPos / scale;
47.             float3 xProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.y, scaledWorldPos.z, textureIndex)) * blendAxes.x;
48.             float3 yProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.x, scaledWorldPos.z, textureIndex)) * blendAxes.y;
49.             float3 zProjection = UNITY_SAMPLE_TEX2DARRAY(baseTextures, float3(scaledWorldPos.x, scaledWorldPos.y, textureIndex)) * blendAxes.z;
50.             return xProjection + yProjection + zProjection;
51.         }
52.  
53.         void surf (Input IN, inout SurfaceOutputStandard o) {
54.             float heightPercent = inverseLerp(minHeight,maxHeight, IN.worldPos.y);
55.             float3 blendAxes = abs(IN.worldNormal);
56.             blendAxes /= blendAxes.x + blendAxes.y + blendAxes.z;
57.  
58.             for (int i = 0; i < layerCount; i ++) {
59.                 float drawStrength = inverseLerp(-baseBlends[i]/2 - epsilon, baseBlends[i]/2, heightPercent - baseStartHeights[i]);
60.  
61.                 float3 baseColour = baseColours[i] * baseColourStrength[i];
62.                 float3 textureColour = triplanar(IN.worldPos, baseTextureScales[i], blendAxes, i) * (1-baseColourStrength[i]);
63.  
64.                 o.Albedo = o.Albedo * (1-drawStrength) + (baseColour+textureColour) * drawStrength;
65.             }
66.  
67.        
68.         }
69.  
70.  
71.         ENDCG
72.     }
73.     FallBack "Diffuse"
74. }
75.