Hi there, lynweiss.
It seems that you've posted similar questions twice. As mentioned above, changing the type from non-inventory to inventory may affect the cost of the items and your financial history.
To avoid messing up your books, you can create a new set of inventory items based on the details of your non-inventory items. Then, deactivate the non-inventory parts to eliminate them from your list. You follow the steps provided by my colleague, DivinaMercy_N to be guided in doing it.
Additionally, here are some resources that will help manage and track your inventory in QuickBooks Dekstop:
I'm just a post away if you have any other concerns or further questions about this topic. Have great rest of the day.
