How to change the volume of these sounds?

The problem with the script is that you are using Volume as if it's a method, try this instead:

local click = workspace.DONOTCLICK
function onClick()
	click.ClickDetector:Destroy()
	local ound = Instance.new("Sound")
	ound.SoundId = "http://www.roblox.com/asset/?id=184417888"
	ound.Parent = game.Workspace.Baseplate
	ound.Volume = 1
	ound:Play()
	wait(5)
	local sound = Instance.new("Sound")
	sound.SoundId = "http://www.roblox.com/asset/?id=174983259"
	sound.Parent = game.Workspace.Baseplate
	sound.Volume = 1
	wait(5)
	ound:Pause()
	wait(110)
	local und = Instance.new("Sound")
	und.SoundId = "http://www.roblox.com/asset/?id=185709952"
	und.Parent = game.Workspace.Baseplate
	und.Volume = 1
	und:Play()
	wait(5)
	sound:Pause()
	wait(220)
	und:Pause()
	local d = Instance.new("Sound")
	d.SoundId = "http://www.roblox.com/asset/?id=317987498"
	d.Parent = game.Workspace.Baseplate
	d:Play()
	d.Volume = 1 
	wait(15)
	d:Pause()
	local go = Instance.new("Sound")
	go.SoundId = "http://www.roblox.com/asset/?id=201111592"
	go.Parent = game.Workspace.Baseplate
	go:Play()
	go.Volume = 1
end

click.ClickDetector.MouseClick:connect(onClick)