how can i get a copy of an ATM surveillance video in California?

I used an ATM at the San Mateo Medical Center in San Mateo, CA, to withdraw money from my out of country checking account, and now I’m in the middle of a legal process and i need evidence that i was there that date at that time, i have my receipt, but thats not enough because the account is not from a USA bank, is there any way i can get a copy of the video surveillance?, do i need to hire an attorney to get this? thanks for your help.
ok here is the deal, i came to the USA in october 2000, i was 15 at that time, i came because my dad had terminal cancer, i was waiting in mexico to get my visa but i couldnt wait no more my dad was going to die, so i came illegally, and for the 7 years that i been in this country i have never been in trouble with the law so my record is clean, now i need evidence that i was here before decenber 21 of 2000 and the only thing that i have is an ATM receipt, because i didnt attend to school the first year i was here, so i need the video to prove that i was there, my dad passed away in may 2003.