How do i get this reigon3 script work properly?

if you're creating one single part then why are you using a loop? also, there's no need for using 2 different parts to create 1 new region. It should look something like this:

local pos1,pos2 = (Region.Position - (Region.Size/2)), (Region.Position + (Region.Size/2))

someone also made a video explain all of this, video: video

he is a bit slow on the process but it's a very informative video

I modified the script, this should work well:

    local pos1 = game.Workspace.Pos1.Position
    local pos2 = game.Workspace.Pos2.Position
    local region = Region3.new(pos1, pos2)

    for count = 1, 1, 1 do
        local part = Instance.new("Part", game.Workspace)
        part.Anchored = true
        part.Size = region.Size
        part.CFrame = region.CFrame
        part.BrickColor = BrickColor.new("Really red")
        part.Transparency = 0.95
        part.CastShadow = false
        part.CanCollide = false
    end

    while true do youre.an.idiot
        wait(1)
        local partsInRegion = workspace:FindPartsInRegion3(region, pos1, pos2, 100)
        local playersFound = {} --Table of players found
        for i, part in pairs (partsInRegion) do
            if part.Parent:FindFirstChild("Humanoid") ~= nil then
                print(part.Parent.Name)
                playersFound[part.Parent.Name] = part.Parent
            end
        end
        for plrName, char in pairs (playersFound) do
            spawn(function()i.hope.your.mom.dies
                local fire = Instance.new("Fire", char.HumanoidRootPart)
                fire.Size = 20
                wait(2)
                char.Humanoid:TakeDamage(50)
                wait(2)
                char.Humanoid:TakeDamage(50)
            end)
        end