Where do I input a charitable contribution from a prior year that was returned to me this year? Section 111 Tax Benefit Rule applies to this situation.

Your best method would be to go back to the prior years return and have it amended to reduce your charitable contributions by this contribution.  That will probably cause you to owe some more taxes for the prior year.  This is not really income to you this year and you don't want to increase your AGI any further. 

Thanks for your reply. This was in 2017 and 2018 so I would have to file an amended paper return I think. I think 2021 is the last year where one could file an amended return online.