How do I make an attack at a player's hand position and face at the mouse?

So, I have a local event for the mouse, a server script for the positioning and a remote event for communication and information.

Local Script:

local rp = game:GetService("ReplicatedStorage")
local event = rp:WaitForChild("RemoteEvent")
local player = game:GetService("Players").LocalPlayer
local Mouse = player:GetMouse()

    Mouse.Move:Connect(function()
        local MousePosition = Mouse.Hit
            event:FireServer(MousePosition)
end)

Server Script:

local rp = game:GetService("ReplicatedStorage")
local event = rp:WaitForChild("RemoteEvent")

event.OnServerEvent:Connect(function(player,mp)
    local beam = player.Character:FindFirstChild("beam")
    beam.PrimaryPart = waterb.Cylinder
    beam.Cylinder.CFrame = CFrame.new(beam.Cylinder.Position, mp.Position)
end)

So I have a laser beam attack model located inside the player's model, so thats why it says player.Character:FindFirstChild("beam"). I sometimes get errors on line 7 about Vector 3 and CFrame but when I don't, the beam just stays still straight up, not facing the mouse position. I also tried mp instead of mp.Position, or tried changing MousePosition in local script to Mouse.Hit.p or Mouse.Hit.Position, but i just don't know what to do. Please help on how my attack can atleast face toward the mouse, or make it so the beam stays at the players hand and direction is controlled by mouse. please help!!!