Well you could ask your doctor but not detected on a viral load test means no hep c virus was detected in your blood meaning you do not have hep c.
But again the best person to ask is your doctor who ordered the test.
So you probably had a hepatitis c antibody test in the past once you test positive for hepatitis c antibodies you will test positive for the rest of your life and yes you cannot donate blood.
You should have had the HCV RNA by PCR at that time to determine if you were currently infected back then. About 25% of people are able to beat hep c infection without treatment. The rest will go on to develop chronic hep c infection and will need treatment to be cured.
If you did not have the HCV RNA PCR test back then it’s possible you beat the infection without treatment.
The test you just had was the HCV RNA by PCR that looks for the virus in your blood your result was not detected which means you are not currently infected with the hep c virus. If you were to have the hepatitis c antibody test based on your previous results you will very likely test positive for antibodies. However, antibodies are not the virus they are made by your body when it tries to fight off an infection.
So even thought you are not infected with the hep c virus you will still test positive for hep c antibodies likely for life.
Best of luck