Copy new rows from source to destination based on criteria

Hello ukcala ,
Power Query and Power BI are designed to read existing data, not to write back to sources.
They also don't have triggers that react to certain events.
But if you're "just" looking for some special logic that has to be applied when you import data from 2 different sources and combine them in a special way before loading to the data model, I'd recommend to post sample data or upload a file with sample data.
Please check out these instructions:

https://community.powerbi.com/t5/Community-Blog/How-to-provide-sample-data-in-the-Power-BI-Forum/ba-p/963216

help how to get your questions answered quickly - Microsoft Power BI Community