Good Day
Had a 15-year battle with my wife’s cancer and she passed at 50 
but only supposed to live a few, squeaky wheel gets the grease.
During and after migration was hell so had to deprioritize, reading old emails now.
Just been using the manual switches etc while the STH-ETH-200 hub has been executing the previously program routines.
How can I migrate this all to the new app keeping as much of the original work as possible?
Appreciate your help!
Paul
let’s start with - Do you remember if you migrated your SmartThings account to a Samsung account? if yes, that may make things easy and I would suggest installing the ST app and logging in with your Samsung account. Check if your hub shows in the app.
If you didn’t migrate to a Samsung account… reply back.
what Country are you in?
I am/was in the United States and signed into my Samsung account and it shows SmartThings under apps and services. Used same account to sign into the SmartThings app and there is no devices listed. Tried to add hub but it’s asking me for a welcome code I don’t have.
Other than that I don’t see where where I migrated.
Last SmartThings email was October 15th 2020
Subject: Thank You! Partially reading “See you soon in the new app!”
The day before email
Subject: Hurry! SmartThings Classic will be discontinued tonight!
The welcome code is easy to get. Post in the following thread and list the serial number of your hub. ST staff generally reply to you with the code when they are available. also check the inside of the battery compartment cover
https://community.smartthings.com/t/smartthings-hub-sth-eth200-welcome-code-missing/281984
I would log into ST Advanced Web App and verify that there are no hubs, devices, or locations there before I attempted to re-add my hub.
Not inside, posted 
In advanced only my location I just added shows under Samsung account. My original login for smartthings.com comes back as no such account
Sounds like you never migrated your original ST account to a Samsung account.