Let's make sure that the Also update this account in historical transactions box is showing as an option, sylvia35.

You'll only see the option once you edit an income account of your non-inventory or service item. I've attached a screenshot so you'll be guided visually.

After you've checked the box, you can now move your historical transactions over to the new account. You'll want to see the screenshots for the detailed steps provided by @MichelleBh.

For your reference, you can run inventory reports in QuickBooks Online so you'll be able to get the information you need. Please read this article for more information: Run Reports In QuickBooks Online.

Please touch base with us if you need further assistance with inventory in QuickBooks Online. We'll always make sure to get back to you.