Hi Gail:

For new items, the basic requirements are:
-Item code
-Description
-Category
-Stock Unit of Measure
-Account Set
-Base (selling) Price

I would export some items using those fields plus any others that you use. Create the file in Excel format then modify the file in Excel to add new items using the existing lines as a sample. Delete the sample lines and import the file.

NB: Do a backup before importing!

As for existing items, it is impossible to import Actual Costs or Actual Quantities so that that removes a source of damaged data.

I would export only the fields I want to change. Keep the file as simple as possible. If the field is listed on Import screen, it should be possible to import it without causing a problem.

If you are in doubt, tell us the fields you plan to import.