How do I detect if an object is in the workspace?

I tried to do

if workspace.Part then print("1") else instance.new("Part").Parent = workspace end

it said Part isn't a member of workspace

If you know the part is either there or isn't there

local Part = workspace:FindFirstChild("PartName")

Or, if you want it as soon as it appears, and it's certain to appear:

local Part = workspace:WaitForChild("PartName")

if Part then
	...
end

• To find if the part exists, use:

if workspace:FindFirstChild("Part") then

• To find if the part does not exists, use:

if workspace:FindFirstChild("Part") == nil then

• Here's a fix to your script.

if workspace:FindFirstChild("Part") then
print("1")
end

if workspace:FindFirstChild("Part") == nil then
Instance.new("Part").Parent = game.Workspace
end