1. Go to the Products Page and click on the name of the Master SKU you would like to change.
2. Click on Adjust SKU and type in your changes then press save.
To Do This in Bulk:
1. Click on import/export and select import SKU adjustments.
2. Download the template and in the first column type in the SKU you want to Change and in the second column type in what you would like to change it to.
3. Import in your changes.