We migrated to QB online. How can set up units of measurement for our products?

You can consider integrating a third-party application to set up your item with their correct unit of measurement, anna118.

Currently, this feature is exclusive to the QuickBooks Desktop version. Since you've migrated to QuickBooks Online (QBO), let's find an app that can assist you with this function:

1. Open your QuickBooks account. 
2. Go to Apps, then select Find apps.
3. Search for the application's name in the provided field, or use the Browse Categories or Browse Industries dropdown to select an app

I'll also include this article if you want to learn how to correct your inventory quantity in QuickBooks: Adjust inventory quantity on hand.

Feel free to reply or post in this forum if you have any other questions about managing your inventory in QBO.

@anna118 

You need a 3rd party inventory management app to sync with QBO. Otherwise, consider switching to QB Desktop Enterprise.