Hi i'm 20 years old can I still get adopted?

Hi i'm 20 years old I was brought from mexico to the USA illegally and i'm just wondering can I get adopted to get residency from my step dad?

It depends on the state laws where you are. In some states adults can be adopted if they have special needs and are unable to care for themselves. If you don't fit that description probably not. However, you can always hire an attorney where you live to look for a loophole. Your biological father would have to relinquish his parental rights if it is found to be possible otherwise.