IRS is asking for corrected 1040x form from my amended 2019 tax return. Thought I sent that form when I initially amended it. What should I do, where do I get the form?

The IRS sent me a letter saying thanks for amending my Dec. 31st 2019 tax return, and that if I used a tax return preparer I needed to give them a copy of the letter along with the corrected 1040x form.  I don't understand the legal jargon and gibberish, but it doesn't seem as though anything else is asked of me in the letter.  I thought that part of the amendment to that return involved me already having sent a corrected 1040x form, so I don't understand what I need to do now.