Please format your code correctly to make it easier to read
local function savePlayerData(playerUserId)
if sessionData[playerUserId] then
playerData:SetAsync(playerUserId, sessionData[playerUserId])
end
end
local function saveOnExit (player)
local playerUserId = “Player_” … player.UserId
savePlayerData (playerUserId)
end
game.Players.PlayerRemoving:Connect (saveOnExit)
Now, to answer your question. It’s recommended to place scripts that run on the server to be placed in game.ServerScriptService.