RitaK,
Those ducklings' lives depend on you. You need to protect them. Every member of the household must commit to keeping them safe from your dog and any other danger.
I am not a dog trainer, but if she has a strong hunting instinct, the best you may be able to do is keep her as far away from the ducks as possible from here on out.
Build the ducks a Little Fort Knox. Know where the Basenji is at all times. If that seems distasteful, then perhaps the ducklings need a new home.
When I was younger, a little cousin came over and repeatedly opened the door to my room, where the ducklings were in an open-topped brooder, and the poodle killed them. That experience left an impression on me. This little cousin was not supervised. By the time I realized what had happened it was too late. Poodles are a hunting breed. I did get more ducklings, but had learned that the poodle - an otherwise sweet, mellow guy - could not control those instincts, and I protected the ducklings and also had learned that all visitors would be assumed to make similar mistakes so I changed the brooder arrangement and access to my room so that it was less likely someone would open the door, and even if the dog got into my room, the ducklings were safe.