It’s called radical sanation… you were close!

I had this done for my then invalid marriage and my anniversary is on the original day of my invalid marriage.
To the OP, ideally it would be the day of your marriage, but if you have a convalidation done for your marriage, then, for the CC, your true anniversary would be the day your convalidation took place, if you do a Radical Sanation, it’d be the day you originally got married. BUT, you cannot sanate your marriage thru this process if there is a way you can do a convalidation. A sanation is only for extreme occassions… here is what Catholic Answers explains:
Radical Sanation