Deleting V2 Option Sets
Before starting this step, you’ll want to take your store down for maintenance. Go to Channel Manager and click the three dots to the right of your store name. Select Deactivate and save.
Because V3 doesn’t use option sets, you’ll have to delete them from your store before the upgrade option becomes available. This is the scary part of the process. Don’t worry, it will all be fine as long as you have the spreadsheet from the previous step!
Go to Products > Options and click on the Option Sets tab. Adjust the number per page so you have the fewest pages. Then use the select all checkbox to select all the options on each page and delete them. Make sure you have deleted them all before moving on to the next step in the V3 upgrade process.