Let's get things taken care of, @lynweiss.

In QuickBooks Desktop (QBDT), changing the types from non-inventory to inventory may affect the cost of the item. This may also alter the file's financial history from the beginning. 

You can create a new inventory item based on the details of the non-inventory. Then you can make the non-inventory inactive to remove it from the list. Allow me to guide you through the process.

To create a new inventory item:

1. Open your QBDT program and click the Lists tab.
2. Next, choose Item List.
3. At the bottom right part of the page, click the Item dropdown.
4. Then, select New.
5. From the Type field, choose Inventory part.
6. Fill in needed details and select OK.

Make non-inventory items inactivate:

1. Navigate to the Lists menu and select Item List.
2. Look for the Non-Inventory item.
3. Highlight the item and select the Item option below.
4. Then, choose Make Item Inactive. 

See this article for more information: Add, edit, and delete items.

QBDT also gives you the ability to add custom fields for specific details about the products and services you sell. Once you create one, you can also add these item fields to sales forms.

Feel free to click the Reply button if you have additional questions about converting non-inventory items to inventory. This way, we can assist you further. Have a good one.