Who can help for the leaderboard script?

all you have to do is create RemoteEvent in ReplicatedStorage this will be your communication channel between LocalScript and Server, then in Script (not LocalScript) you need to do a code like this:

local players = game:GetService('Players')
local replicatedStorage = game:GetService('ReplicatedStorage')

players.PlayerAdded:Connect(function(player)
    if player then 
        local folder = Instance.new('Folder')
        folder.Name = 'leaderstats'
        folder.Parent = player
        local JumpPwr = Instance.new ('IntValue')
        JumpPwr.Name = 'JumpPwr'
        JumpPwr.Parent = folder
        JumpPwr.Value = 0
    end
end)

replicatedStorage.RemoteEvent.OnServerEvent:Connect(function(player)
  if not player.Character then return end
  local humanoid = player.Character:FindFirstChildOfClass("Humanoid")
  if not humanoid then return end
  if humanoid.FloorMaterial == Enum.Material.Air then return end
  print(player, "JumPED")
  player.leaderstats.JumpPwr.Value += 1
end)

this event will be triggered when LocalScript triggers, LocalScript will trigger it when you press the button, that means in your LocalScript you have to stuff like this:

local replicatedStorage = game:GetService('ReplicatedStorage')

script.Parent.MouseButton1Click:Connect(function()
    local player = game.Players.LocalPlayer
    local character = player.Character
    local humanoid = character.Humanoid
    if humanoid.FloorMaterial == Enum.Material.Air then return end
    humanoid.JumpHeight += 1
    --player.leaderstats.JumpPwr.Value = player.leaderstats.JumpPwr.Value + 1 
    -- this will trigger the RemoteEvent on server
    replicatedStorage.RemoteEvent:FireServer()
    local oldJumpPower = humanoid.JumpPower
    humanoid.JumpPower = 10
    humanoid:ChangeState(Enum.HumanoidStateType.Jumping)
    humanoid.JumpPower = oldJumpPower
end)

if you done with this then there is important issue that is that exploiters can spam :FireServer which will give him BIG jump power, in order to avoid that you should also check on Server whether player.Character.Humanoid is not in Air as you did in LocalScript.