You can install the trial (demo) of Endnote 20 and use all of Endnotes functionality. After the trail period, however, EndNote 20 reverts back ta a reference viewer only.
With this said none of your work is wasted.
As soon as you buy an Endnote license you can unlock your trial to full functionality again, with all the references you added. You can buy an Endnote license here https://www.alfasoft.link/buyendnote
As soon as you have your product key, in Endnote click on Help>Activate EndNote