why this not gives a level when xp value pass 100?

Hello, gloveshun!

You can check once a value has went above your selected value using the changed event. This event will fire everytime a value has changed. Also, you wouldn't need a remote to give the player a level as this is in a normal script.

UPDATED SCRIPT:

game.Players.PlayerAdded:Connect(function(plr)  

    plr.leaderstats.XP.Changed:Connect(function(NewValue)
        if NewValue >= 100 then
            plr:WaitForChild("leaderstats").Levels.Value = plr:WaitForChild("leaderstats").Levels.Value + 1 
        end
    end)


    plr.Chatted:connect(function(msg)
        if msg == "/e dance" or msg == "/e dance2" or msg == "/e dance3" then
            plr.leaderstats.XP.Value = plr.leaderstats.XP.Value + plr.leaderstats.Levels.Value
            repeat
                plr.leaderstats.XP.Value = plr.leaderstats.XP.Value + 10
                wait(5)
            until plr.Character.HumanoidRootPart.Velocity.Magnitude >= 2
        end
    end)

end)