Visitor visa for people who had Green Card or Abandoned green Card

[kamit]

I in in a quite confusing situation while filing visitor visa for my Mother in law and filling her previous US travel information on DS - 160
Both of my father in law and mother in law were on Green Card in US around 22 years ago after then they decided to stay in India as many decide to go back
US Embassy asked father to return his green card during his next travel on visitor Visa9again many years ago) however about my mother in law , she is not sure weather or not they returned Green Card to US Embassy and they are also not carrying their Green Card now with them too(as usually happens in India, old people don't use to manage documents for long).

I am in awkward situation . I have their old passport where a U number(above stamp of visa number) is printed and a date is marked

In DS 160 -> previous US travel -> i have to fill visa number and date of issue of visa ...

Can i fill U number(which is printed as Visa number on her old passport) and date mentioned on passport. I am not sure if U number is same the visa number

The whole issue is with her age and she is not able to determine all about her documents and dates and her old passport is only source of information

I will really appreciate any help in this regard

[immihelp]

Yes, you can put that number.