Which visa office for refugees/IMM5540 question #9

[egosheep]

On the 5540 where it says, "Which Canadian visa office issued your immigrant visa or confirmation of permanent residence?", my wife was 6 years old at the time and I believe she came to Canada with her parents as refugees from El Salvador.  She doesn't have any of the old forms or entry documents.  I have the date she became a Citizen, but she was too young at the time to remember what all the processes were.  Any advice on how I should proceed here?