PR application, fingerprint part

[beautifulday1]

Hi everyone,
I have forgotten my fingerprint details. I even can’t remember the year. Could you please advise me what should I do to fill this part. At this moment I am thinking to put “ I cannot remember” in every section of that part. Is it okay to put something like this? Thank you advance for your help.

[marcsiga]

I am not expert but I would put stars there and include An explanation in the covering letter.
I guess they will be able to track it back..

[beautifulday1]

Thank you very much for your opinion. Much appreciated