How do I change Keyclick To mouse click?

What you're doing is wrong. You're trying to check if the input's UserInputType which is an event, not an enum. You don't need to use UserInputService.InputBegan if you will change it to a mouse click. Replace that event with script.Parent.MouseButton1Click event.

local player = game.Players.LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()

script.Parent.MouseButton1Click:Connect(function()
    local part2 = Instance.new("Part", workspace)
    part2.CanCollide = false
    part2.Anchored = true
    part2:PivotTo(character:WaitForChild("Head"):GetPivot() * CFrame.new(0, 0, 5))
    part2.Name = "Part1"

    character:WaitForChild("Humanoid"):MoveTo(part2.Position, part2)
end)

But if you want both for "E" and button (i assume for pc and mobile) you can create one function and connect that function to the two events (UserInputService.InputBegan and GuiButton.MouseButton1Click) altogether in one script (make sure that script is inside the button).

local player = game:GetService("Players").LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()
local UserInputService = game:GetService("UserInputService")

function MovePlayer()
    local part2 = Instance.new("Part", workspace)
    part2.CanCollide = false
    part2.Anchored = true
    part2:PivotTo(character:WaitForChild("Head"):GetPivot() * CFrame.new(0, 0, 5))
    part2.Name = "Part1"

    character:WaitForChild("Humanoid"):MoveTo(part2.Position, part2)
end

UserInputService.InputBegan:Connect(function(input)
    if input.KeyCode == Enum.KeyCode.E then
        MovePlayer()
    end
end)
script.Parent.MouseButton1Click:Connect(function()
    MovePlayer()
end)