How to save tables: Datastore?

Um.. yes. I Love that spelling of yours.

Anyways... I don't know much on this, but here are the links, I can also provide an example or of something that I know.

JSON Format

JSONEncode() function transforms a Lua table into a JSON object or array and CANNOT ncode anything other than strings, numbers, tables, and booleans, anything else would error.

JSONDecode() function transforms a JSON object or array into a Lua table.

HttpService() allows HTTP requests to be sent from game servers.

Anyways, i'll show you an example I have, assuming that you already know what DatastoreService is.

We already have everything set up, and it should look something like:

local PlayerData = {
    Player = {Coins = 0, Level = 0, Diamonds = 0, Kills = 0};
}

game.Players.PlayerAdded:Connect(function(plr)
    local key = "User_"..plr.UserId

end)

game.Players.PlayerRemoving:Connect(function(plr)
    local key = "User_".plr.UserId

end)

Okay so, what I would do is check to see if player has any existing data, if not then load the data they had previously. (checking to see if they have a prev key.)

-- Inside of player added.
if Datastore:GetAsync(key) ~= nil then
    -- assign data
else
    -- load prev data
end

Then you'd want to assign the table to the player:

PlayerData[plr] = PlayerData

and load previous data which we'll be wrapping in pcall, to find any errors (I usually kick to prevent overlapping of data/loss of it, but you can return it instead..):

local suc, msg = pcall(function()
    wait(5)
    PlayerData[Player] = HttpService:JSONDecode(DataStore:GetAsync(Key));
end)
if not suc then
    Player:Kick(msg)
end

Whenever the player IS leaving, you'd have something like (remember I am wrapping in pcall for any errors.):

local success, message = pcall(function()
    if PlayerData[Player] ~= nil then
        DataStore:SetAsync(key, HttpService:JSONEncode(PlayerData[Player]))
        print('Player Data set.')
    end
end)
if not success then
    print('Error: '..message)
end

I suggest reading what I had above before even using my code, as I didnt explain the proces of it. Hoping that you'd just 'understand' what were getting here (also not going to lie, im bad at explaining things too.)

Welp, hope this helped. Have a nice day!