Depending on your county of residence, the "cause number" most likely refers to number given the cause of action pending in court. Most counties call such a number a "case number," but some places choose to call them some other name, such as cause of action.
If the answer is not satifactory, you should contact a local attorney in your area. You may be able to find such an attorney at attorneypages.com. If you are in central Ohio, then visit our website at www.jmoserlaw.com .Good luck.