First of all, are you sure your parents don't have it some place with their important personal papers?
First, you got to figure out where you were born and go to that city, county or state's office of Dept. of Health, or County clerk's office. Once you determine that, the do a search for a website for the jurisdiction you need to get it from. Usually most government websites that have those records will state the procedures you need to do to get such records and the fees charged. You may have to do in it person, produce some form of ID
and have at least one of your parents with you. What you want is a "Raised letter seal"/official/original replacement certificate. Check the US State Department website (do a web search) for the forms and instructions for application for a passport. You will have to apply in person to a government authority, such as a County clerk, or selected post offices. See the State Dept. website section as to where you go for your initial filing. You will have to have at least one parent with you when you apply, and if under a certain age, BOTH parents need to accompany you due to laws to limit child abductions in nasty divorce situation.