The SKU option is available in all QuickBooks Online versions, Yvonne. You should be able to enter the SKU number when creating a product/service item.
To display the SKU column when creating a transaction, you'll need to turn on this function first. Here's how to do it:
If you're having issues entering or displaying the SKU, I'd recommend doing the browser troubleshooting steps. This will help us get rid any cache-related issues. Here's how to do it:
Get back to me if you need more help with this. I'll be around.