For me, Baseplate isn't in workspace. What is that?

It doesn't work. I created my function, I checked the function, but it says when I try to use it on baseplate, baseplate isn't (game.workspace.baseplate) Why is that?

Lua is a case-sensitive language. workspace.baseplate doesn't exist by default, but workspace.BasePlate does, because of the capitalized 'b' and 'p'.

It's BasePlate, always check your capitals. Now, make sure your function is correct.

local BasePlate = game.Workspace.BasePlate --What BasePlate is.

function DoSomethingWithBasePlate() --Creates a function to do something with BasePlate.
	BasePlate.Transparency = 0.5 --This only changes the transparency of BasePlate, only an example.
end

DoSomethingWithBasePlate() --Calls the function, always remember to do this when using functions.

You can either check the names of the children in the parents of the parent indicated "Workspace" by saying print(unpack(game.Workspace:GetChildren())) or as normally check in your robloxstudio and just change the name or as in script builders you would just do game.Workspace.BasePlate -- the current name changed to game.Workspace.BasePlate.Name = "Baseplate"

Try game.Workspace.BasePlate.