My Worlds Are Gone PLEASE HELP ME

When i update my minecraft all of my worlds are gone. I can't handle it. My all labors are deleted. What can i do? I searching my files and i find my worlds' files in there. But they are not in the system i think. Please help me dear Mojang team. I work really really hard for create and build this worlds i built big cities. I tried to do this from one year and now my all works are trash. I am speechless, im really sad and upset. Please help me. Please solve my problem because i don't know what can i do. I want my worlds back. They are my babies. I feel like my babies are die. Please Mojang Minecraft team please hear my voice and help me...