How do I know if I'm eligible for any of my ex-husband's pensions now that he is retiring?

If any of these pensions vested between the date of marriage and the date of separation, probably you have an interest. However, I am curious as to whether you preserved this interest when you signed off on the divorce. Usually, as part of the divorce, the pensions are split up via the QDRO process. I hope you didn't sign a marriage settlement agreement in which you waived all your rights to his property.