table.insert not working properly, or how I want it to?

So, essentially I have a datastore, fire a BindableEvent to my leaderboard, which has the players purchase history, the history is a table which is filled with strings by using unpack(table) the history is set using the event and then upon a GUI button fires an event that goes to the leaderboard with the ID which is a string that is a variable inside the GUI's button's script, that is then inserted into the table, using table.insert, however it clears out the previous thing in there, is there a way to get around this or, what am I missing, also, will the:

if id == chardata then 
--do code
else
--do code
end

scan through the entire number of strings provided if not, would I use a: for _, k etc. to see if the the strings match the id the GUI button provided?

EDIT: Would it be easier to unpack a table unpon the player joining, or save all of the history as strings, because of the limit a datastore can hold? Also, how many strings can it hold, as I plan on this holding about 100-200+ overtime, all will be about 5-12 characters long, if that is needed.

Leaderboard:

--This event handles all the GUI button purchases.
moneye.Event:connect(function(cost, plr, id)
    if cost <= playerLeaderstats[plr]["Cash"] then
    local user = "User_" .. plr.userId
    local saves = Characters:GetAsync(user)
    local chardata = saves
    print(id,"id should be " .. chardata )
    if id == chardata then  --This is the line I have the question above on, since there will be more than one string will it automatically search through all of them or not?
    --print(unpack(history), "TESTETET")
    return print("[System]: Already bought.")
        else
    playerLeaderstats[plr]["Cash"] = playerLeaderstats[plr]["Cash"] - cost
    cashe:Fire(playerLeaderstats[plr]["Cash"])
    print(unpack(history[plr]), "b4 insert")
    table.insert(history[plr], id) --Error is here, it overwrites the previous string inside the table, how do I make it not do that?
    print(unpack(history[plr]), "after insert")
    Characters:SetAsync(user, unpack(history[plr])) --This assures the the table will be packaged as all strings, the strings will then load next time the player joins so they can't re-purchase a product they already have, the whole reason for inserting the ID into a table then saving it to a datastore.
    print(saves, "after setasync")


            end
        end
    end)    


--This event is the event fired from the datastore
    historye.Event:connect(function(data, plr)
        if plr.userId == player.userId then
        print("received")
        print(data)
        print(unpack(history[plr]), "before")
        local insertthis = data
        table.insert(history[plr], insertthis)
        print(unpack(history[plr]), "after")
        else
            return print("error")
        end

    end)

GUI Button:

script.Parent.MouseButton1Click:connect(function()
    local tofire = plr:FindFirstChild("Events").MoneyTransfer
    local id = "TestA"
    tofire:Fire(COST, plr, id)

end)

If any more code is needed I will provide it, thanks for any help.