You never declared what the camera was in the tweenInfo. This is the new version.
local mainMenuMap = workspace:WaitForChild("MainMenuMap")
local tweenService = game:GetService("TweenService")
local btn = script.Parent
local currentCamera = game.Workspace.CurrentCamera
currentCamera.CameraType = Enum.CameraType.Scriptable
local function tweenCamera(pos,tweenTime)
tweenService:Create(currentCamera,TweenInfo.new(tweenTime,Enum.EasingStyle.Linear),{CFrame = pos.CFrame}):Play()
end
btn.MouseButton1Click:Connect(function()
btn.Visible = false
btn.Parent.TextLabel.Visible = false
tweenCamera(mainMenuMap.CameraPart2,1)
wait(1)
print("Reached Destination")
end)