How to create an only rank uniform?

Hi, Can someone help? I tryied to script an only rank uniform Script, but it doesn't work.

Would work something like this in a server script.

local RankId == 254 --rank id 0-255 check group configure or use https://api.roblox.com/groups/{groupIdhere}

game.Players.PlayerAdded:Connect(function(player)
	plr.CharacterAdded:Connect(function(char)
		if plr:GetRankInGroup({GROUP_ID}) == RankId then
			local Humanoid = character:WaitForChild("Humanoid")
			local HumDesc = Humanoid:GetAppliedDescription():Clone() 
			HumDesc.Shirt = {ShirtId} 
			HumDesc.Pants = {PantsId} 
			Humanoid:ApplyDescription(HumDesc)
		end
	end)
end)