Hi RobynM1,
To answer your actual question, you can do this manually one by one, you can also do this via import. The problem you will face using either method is that once an item has been used in a transaction, this setting can no longer be changed - at least not by the user.
Your options would be to renumber each item manually (zzItemx) and make inactive, then import new items with the desired settings, or get MYOX Services to change the 'I Inventory' setting for you. They can do this for existing items, whether used or not.
Regards
Gavin
gavinw222@gmail.com