LookVector on CFrame not working on viewport frame?

Hello I am trying to do a viewport frame script. The problem is when i'm using a CFrame for a camera for the viewport frame this happens

14:28:09.213 - game.Workspace.Viewportcam.CFrame = game.Workspace.Cam.CFrame.LookVector:1: invalid argument #3 (CFrame expected, got Vector3) 14:28:09.215 - Stack Begin 14:28:09.225 - Script 'game.Workspace.Viewportcam.CFrame = game.Workspace.Cam.CFrame.LookVector', Line 1 14:28:09.227 - Stack End

What I want to achieve is there is a part above the viewport frame that the camera will face In front of. Now I actually do know that look vector is meant for vector3 but is there a way to use it in a CFrame? Here is the code

game.Workspace.Viewportcam.CFrame = game.Workspace.Cam.CFrame.LookVector * 5
game.StarterGui.SurfaceGui.ViewportFrame.CurrentCamera = game.Workspace.Viewportcam
game.Workspace.Viewportcam.CameraType = Enum.CameraType.Scriptable
game.Workspace.Viewportcam.CameraSubject = game.Workspace.Cam

for i,v in pairs(game.Workspace:GetDescendants()) do
	if v:IsA("BasePart") then
		local vclone = v:Clone()
		vclone.Parent = game.StarterGui.SurfaceGui.ViewportFrame
		game["Run Service"].RenderStepped:Connect(function()
			vclone.CFrame = v.CFrame
		end)
	end
end

For some more info

The local script is in replicated first

Camera is in workspace

Gui is a SurfaceGui (I could use billboard but I want to use surfacegui for this case.)

But in advance thanks!