You must wait.

The listings have been used up.

Even if you were to list  a few and end them immediately because you decide to list other products, they count against the 40.

But if you list 40 and select the 3 free auto relists on all that in effect gives you 160 free per month if they don't sell.

But naturally it's only for 40 items.

Edit - Seems there are others up this late.