How can i datastore an leaderstats stringvalue?

As far as I am aware, you cannot save a string value. What I would suggest is to have the Rank be a IntValue also, then have a separate script that loads something like

local function onPlayerJoin(player)
	    local leaderstats = Instance.new("Folder")
	    leaderstats.Name = "leaderstats"
	    leaderstats.Parent = player
	 
	    local Clicks = Instance.new("IntValue")
	    Clicks.Name = "Clicks"
	    Clicks.Value = 0
	    Clicks.Parent = leaderstats
	 
	    local Prestiges = Instance.new("IntValue")
	    Prestiges.Name = "Prestiges"
	    Prestiges.Value = 0
	    Prestiges.Parent = leaderstats
	 
	    local Gold = Instance.new("IntValue")
	    Gold.Name = "Gold"
	    Gold.Value = 0
	    Gold.Parent = leaderstats
	 
	    local Rank = Instance.new("StringValue")
	    Rank.Name = "Rank"
	    Rank.Value = "Noob"
	    Rank.Parent = leaderstats

            local RankSave = Instance.new("IntValue")
	    RankSave.Name = "RankSave"
	    RankSave.Value = 0
	    RankSave.Parent = leaderstats
end

game.Players.PlayerAdded:Connect(onPlayerJoin)

then save the "RankSave" instead of the "Rank"

then I would use a script that runs in a playerGui (I like to do that because it can make and detect changes to server)

the script would read

wait (2) --gives time for data to load

onchange() --this will run the script once so that it loads up one time without detecting a value change

function onchange()
      local ranksave = script.Parent.Parent.leaderstats.RankSave
      local rank = script.Parent.Parent.leaderstats.Rank
      if ranksave.Value == 0 then
      rank.Value = "Noob"
      
      --Continue else if for all ranks you want to have     

      end
end
script.Parent.Parent.leaderstats.RankSave.Changed:Connect(onchange)

then as the game goes on, change the ranksave instead of the rank and this script can change the rank string value.

I hope this helps and makes sense!