If these were originally intended to be a simple list at the end (i.e. endnotes), you used the wrong feature.

Inserting the notes manually may be difficult, but it is not impossible.
It is simply tedious. I can understand your frustration.

There is no process or method built into Word to transform a numbered list referenced using the cross-reference feature into endnotes.
Might it be possible to write a macro that would do this? Yes.

If what you have is a simple numbered list to which you have scattered cross-references to the number in your document (i.e. endnotes without using the endnote feature) I would suggest posting a separate question in the Word VBA Forum with a link back to this one asking for help doing that. The title should be something like "Transform cross-references to numbered list into endnotes using vba."