Are you asking what AGI to use for your 2020 return so that you can e-file? If you filed a joint return for 2019 the amount on line 8b is still your 2019 AGI even though you are not married now. If you do not have a copy of that return you can try to use zero. If zero will not let you e-file you will need to print sign and mail your 2020 return.
You do not put anything on your own return about your ex-spouse.
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
