How to save model positions?

On line 7 it prints -18.929458618164

Im getting this error on line 8 but im not sure what to do or what it means.

-18.929458618164 is not a valid member of Folder

Remote Function script

local ItemStore = game:GetService("DataStoreService"):GetDataStore("Items")

game.Players.PlayerAdded:connect(function(player)
local objects = ItemStore:GetAsync("Details" .. player.Name) or {}
if objects ~= nil then
for i = #objects, 1, -1 do
    print(objects[1])   
    local Item = game.ServerStorage.Items[objects[i-3]]:Clone()
    local coord1 = objects[i-2]
    local coord2 = objects[i-1]
    local coord3 = objects[i]
    Item:SetPrimaryPartCFrame(CFrame.new(coord1,coord2,coord2))
    Item.Parent = game.Workspace
   	 end
	end
end)

local function Saving(player, PositionX, PositionY, PositionZ)
	local objects = ItemStore:GetAsync("Details" .. player.Name) or {}
	print(PositionX)
	print(PositionY)
	print(PositionZ)
    local findItems = workspace.Placed:GetChildren()
    for i = #findItems, 1, -1 do
    table.insert(objects,i-2,tostring(findItems[i].PrimaryPart.Position.X))
    table.insert(objects,i-1,tostring(findItems[i].PrimaryPart.Position.Y))
    table.insert(objects,i,tostring(findItems[i].PrimaryPart.Position.Z))
    end
    ItemStore:SetAsync("Details" .. player.Name, objects)
end

game.ReplicatedStorage.Saving.OnServerInvoke = Saving

Gui Script

script.Parent.MouseButton1Click:connect(function()
    local findItems = workspace.Placed:GetChildren()
    for i = #findItems, 1, -1 do
	game.ReplicatedStorage.Saving:InvokeServer(findItems[i].PrimaryPart.Position.X, findItems[i].PrimaryPart.Position.Y, findItems[i].PrimaryPart.Position.Z)
    end
end)

Okay so for what I know, that isn't the error, the error is, for the InvokeServer, it should only work for the client and not for the actual game so if you can change it, this script would work..

http://wiki.roblox.com/index.php?title=Remote_Events_and_Functions