IK hand

local player = game.Players.LocalPlayer
local character = player.Character or player.CharacterAdded:Wait()
local humanoid = character:WaitForChild("Humanoid")

local rightArm = character:WaitForChild("Right Arm")
local rightHand = character:WaitForChild("RightHand")

local target = workspace.Target -- the part or position you want the arm to reach

local lengthUpperArm = rightArm.UpperArmLength
local lengthForearm = rightArm.ForearmLength

while true do
    local distance = (target.Position - rightHand.Position).Magnitude
    if distance > lengthUpperArm + lengthForearm then
        local targetPosition = target.Position - rightArm.CFrame:VectorToWorldSpace(Vector3.new(0, lengthUpperArm, 0))
        humanoid:MoveTo(targetPosition)
    else
        local targetRotation = CFrame.lookAt(rightHand.Position, target.Position)
        rightArm.CFrame = targetRotation * CFrame.new(0, -lengthUpperArm, 0)
    end
    wait()
end