To be adopted as a child of God means our earthly life is dead with Christ on the cross. Now it is alive with God in Him.

I am in Him, and He is in me.  Like marriage, the two have become one. A oneness has been established. Everything of mine belongs to God, and everything that God has belongs to me. That’s how covenant works. 

To be found in Him, not having a righteousness of my own from the law. But a righteousness through faith. It's not what I have achieved, my religious performance, devotions, or appearance.  It has everything to do with faith in what God has done.