The following guide explains how to show different order number formats for different sales channels.
This feature is available in the Professional, Premium and Managed subscriptions of One Stop Order Processing.
If you want to use a different prefix for the order number for different sales channels you can use the following approach.
For Amazon orders use an order number prefix of AMZ, for Ebay orders a prefix of EBY and all other orders an order number prefix of OTH
Create a new custom fixed field and set its default value to:
[%Sales source%][=]Amazon-SC[AMZ[%Order number%]][[%Sales source%][=]Ebay[EBY[%Order number%]][OTH[%Order number%]]]
You will need to have Order Number and Sales Source in the view.