Subpoena Help for Arrears

My question involves a child custody case from the State of: California. Last month my ex wife lost her job and went on cash aid and welfare assistance. Naturally the Dept of Child Support comes after me for healthcare and child support, and they also find an old order that was never modified. So they say I owe arrears on a time period from 2/09-5/10 for 850 a month. However I did pay her money during that time period but unfortunately I lost all my bank statements from that time during a fire. So now my bank says they can only go back 7 yrs on the customer service computers but if I want the old archived files I have to subpoena the records. I can't afford an attorney and pretty much do everything on my own. I was hoping this forum can help me write something up or help me with the proper verbiage on subpoenaing my own bank records. How do I word it so it is official and doesn't get rejected. Thanks

Subpoena Help for Arrears