How can I stop worring about my two adult kids doing hard drugs every day? I know a lot of kids died from this. We are all in the church of Christ and Christians.
I'm sorry to hear that your children have fallen away and are caught up in the trap of drugs. That you should be concerned about them and the fact that they are lost in sin is proper. "Besides the other things, what comes upon me daily: my deep concern for all the churches. Who is weak, and I am not weak? Who is made to stumble, and I do not burn with indignation?" (II Corinthians 11:28-29).
Worry is a useless action. You get worked up over what you cannot control and cannot change. What you need to do is separate what you can do and what is out of your control.
You can't make your children stop using drugs. But you can encourage them to get themselves sober. You can remove your support of them while they are using. This is one reason many drug users never get motivated to change. Their family shields them from most of the consequences of their sin and they get comfortable with the status quo.
Most importantly you can pray for them that the Lord causes them to realize the danger they are in before it is eternally too late.