If these are U. S. Savings bonds you only show the interest income only, and not as a bond sale.
You would have to click on that you have more boxes on the 1099INT in the interst income area, and it will show Savings Bond interest.
If this is a bond held and then sold, you report it under the investment section. If you don't know the cost basis, you would have to enter $0, unless you can get a cost from the donor.