New plant and Salesorg. implementation and convert salesorders of existing plant

Hi,

Currently we are working with salesorders which are booked in a certain plant xxx with salesorg xxx

We have MTS and MTO scenarios applicable.

For reasons of alignment with other plants in the group we want to implement a new plant which is following a new aligned scenario which is already in place in plant aaaa and bbbb

Therefore we will implement a new plant but need to have a conversion scenario for the existing salesorders in which we have the following rules.

1. If production orders are already started, salesorders can remain as is.(plant xxxx and salesorg xxxx)
2. If production orders not yet started we should convert to new salesorder using new plant and new salesorganisation. (yyyy) and new plant (yyyy)

What is the best way to do this and how to trigger the corresponding data?

I have only 2 years of experience in SAP and this question came up recently.

Thanks for repyling.