Edit Order currently doesn't have bulk editing capabilities.
There are a few bulk actions you can do with Shopify. You can find more information about this in this detailed article from Shopify's Help Center:
Using bulk actions in your Shopify admin.
Our best suggestion would be to work with a developer/Shopify Expert so they can write a one-off program to help you get this done.
Any questions? Reach out to us at firstname.lastname@example.org