i-130: need help on Q.D-2: filing for other aliens

[tan49]

i'm filling out the i-130 for my mom, who's being petitioned by my grandma (her mother, a citizen). the thing is, she petitioned for my uncle before, but do not remember the date. (question D-2: Have you ever filed a petition for this or any other alien before? If "Yes," give name, place and date of filing and result.) what should i do with this question then? thanks a bunch.

[immihelp]

Try to find out the date and mention that date over there.