Trying to get trees to spawn and all the parts generate, but the meshes only go to one!?

when you create the tree, give it a mesh. right now you're picking a single tree (workspace.TreeG) and putting a mesh inside of that tree only i explained more in the comments

math.randomseed(tick()) --Will 'randomize' our pseudo-random num generator.
print(math.random()*4000)
local check_height = 100 --Makes sure trees wont spawn Over the designated Y axis pos.
local map_x, map_z = 4000, 4000 --Define map size.
local num_trees = 2000 --How many trees to be spawned.

--Now, lets use a loop to set how many trees will be placed.
for i = 1, num_trees do 
	--find a random position on the map to place tree
    local rand_x = math.random()*map_x
    local rand_z = math.random()*map_z
	local rayStartPosition = Vector3.new(rand_x, check_height, rand_z)

	--raycast downwards 300 studs from specified start position to find the height of the position we picked
    local ray = Ray.new(rayStartPosition, Vector3.new(0, -1, 0)*300)
    local instance, position = workspace:FindPartOnRay(ray, nil, false, true)

	--if the random position we found is terrain, then create a tree and give that tree a mesh
    if instance and instance:IsA("Terrain") then
		--create a tree
		local NewTree = Instance.new("Part")
		NewTree.Parent = workspace
		NewTree.Position = Vector3.new(rand_x, position.y, rand_z)
		NewTree.Anchored = true
		NewTree.CanCollide = false
		NewTree.Transparency = 0.012
		NewTree.Name = ("TreeG")
		
		--give that tree a mesh, putting the mesh inside the tree we just created
		local NewTreeBody = Instance.new("SpecialMesh")
		NewTreeBody.Parent = NewTree 
		NewTreeBody.MeshId = ("rbxassetid://2640968479")
		NewTreeBody.TextureId = ("rbxassetid://2640968592")
		NewTreeBody.Offset = Vector3.new(0, 36, 0)
		NewTreeBody.Scale = Vector3.new(4, 8, 4)
    end
end