Get (Halachic divorce) from a non-Jew?

Forty years ago I was married to a non Jew and then got divorced. Then I married my present husband was told I do not need a get. My son a baal teshuvah knows nothing of any of this. I am worried when I die he will find divorce certificate and marriage cert with his Dad stating this is my second marriage will wonder if I should have gotten a get. I cannot find my first husband to sign some proof he was and is not Jewish. I could tear up divorce certificate no need for it now. My marriage cert still states this was my second marriage.