My mom got pregnet at 16 and she gave my sister up for adoption in a closed adoption and in FL now I'm 23 and want to at least know who my sister is and my mom would like to know but we have no why of finding out if someone could please help me on how to at least find her or an address please let me know

What year was she placed? What have you already tried for searching?

What does your mom know about it? Was it though a agency or private arranged? Has your mom ever left a letter with the county and birth records, many allow a letter to be left, in case the other party comes looking.

Have she or you posted on any of the dozens of adoption web sites.