CFrame:lerp() Not Working. Any help?

Here's a fixed version of your script:

while true do
    local newCFrame = CFrame.new(script.Parent.Parent.Torso.CFrame.p + Vector3.new(0, 3.5, 3))
    local parentCFrame = script.Parent.CFrame

    script.Parent.CFrame = parentCFrame:lerp(NewCFrame, 0.5)

    wait(0.5)
end

Here's what I changed:

Firstly, I changed this line of code

local NewCFrame = CFrame.new(script.Parent.Parent.Torso.CFrame.X, script.Parent.Parent.Torso.CFrame.Y + 3.5, script.Parent.Parent.Torso.CFrame.Z + 3)

into this:

local newCFrame = CFrame.new(script.Parent.Parent.Torso.CFrame.p + Vector3.new(0, 3.5, 3))

Rather than creating a CFrame with just raw numbers, you can also create one with a Vector3. So, the new operation does some Vector3 math and then creates a CFrame from the result.

Finally, you had this line of code:

script.Parent.CFrame:lerp(NewCFrame, 0.5)

Which was changed to

script.Parent.CFrame = parentCFrame:lerp(NewCFrame, 0.5)

The reason the old one wasn't working is because lerp is a function of CFrame. Just using lerp doesn't move an object, it returns a CFrame lerped between two CFrames.

That's why you also need to set the CFrame of the object you want to move to what you calculate with lerp.

I hope this helps. Good luck!