"make a combat system with a classic sword swing, block and a parry tell me where to put the code"

-- ServerScriptService 
local Players = game:GetService("Players")

Players.PlayerAdded:Connect(function(player)
    local sword = game.ServerStorage.Sword:Clone()
    sword.Parent = player.Backpack
end)

-- Sword Script (inside the sword model) 
local sword = script.Parent
local debounce = false
local blocking = false
local parrying = false

sword.Equipped:Connect(function(mouse)
    mouse.Button1Down:Connect(function()
        if not debounce then
            debounce = true
            sword.Handle:FindFirstChildWhichIsA("Animation"):Play()
            wait(0.5)
            debounce = false
        end
    end)
    
    mouse.Button2Down:Connect(function()
        if not debounce then
            debounce = true
            blocking = true
            sword.Handle:FindFirstChildWhichIsA("BlockAnimation"):Play()
            wait(0.5)
            debounce = false
            blocking = false
        end
    end)
    
    mouse.Button3Down:Connect(function()
        if not debounce and not blocking then
            debounce = true
            parrying = true
            sword.Handle:FindFirstChildWhichIsA("ParryAnimation"):Play()
            wait(0.5)
            debounce = false
            parrying = false
        end
    end)
end)

sword.Unequipped:Connect(function()
    sword.Handle:FindFirstChildWhichIsA("Animation"):Stop()
    sword.Handle:FindFirstChildWhichIsA("BlockAnimation"):Stop()
    sword.Handle:FindFirstChildWhichIsA("ParryAnimation"):Stop()
end)

-- You need to put the first script in ServerScriptService and the second script inside the sword model in ServerStorage. Also, make sure to replace "Animation", "BlockAnimation", and "ParryAnimation" with the actual names of your animations.