Is it possible to change the item type ? From Non inventory to service. Need to update them as they're created with wrong item type

No once an item is created you cannot change the item type Except there is a function to change from non-inventory to inventory item. But that’s all I’ve seen We always have to rename the old item (the non inventory item in your case) as “(item number)-OLD” then recreate the item using the same item number but with the correct item type