How to restore previous SKU

[dettequiaoit]

Hi, my name is Dette. This is emergency and I badly need your help and assistance. Can someone help me how to recover "old/previous SKUs" that were already inputted in all the items. I did try to install an app called "SKUGEN" to generate an SKU, but only for the additional items that were still on draft. It's the items that doesn't have any SKU or barcode right from the supplier, but since it is needed to be filled out I explore and research, and that's what I found on Youtube that could help me create an SKU. I didn't know it could affect the whole store because right now, nothing in the store scans. And I'm super worried!!! Because even I did install it to test, I just tried it to see if that will work out for the items I just added on draft but not for the whole including active ones. So, I am paranoid now. I don't know what to do. I just uninstalled the app to see if the SKUs will be recovered but everything has changed. Please help me!!!