BP 140/90 is a bit too high for a young man. At your age, your blood pressure should be about 120/80.
However, one single monitoring at the doctors office can be falsely high. If you are concerned about your blood pressure, ask for a 24 hour monitoring.
A blood pressure of 140/90 will not cause EKG changes, especially not flattened T waves. I wouldn't worry about a flattened T wave in lead V6, but ask your doctor just to be sure.
I have BP 140/90 is it indicate as pre hypertension and also confirm is this effected the T wave V6?
The numbers look normal to me.
I'm not sure which significance the flattened T wave has. Probably a non-specific finding (not indicating any specific disease) but you may ask your doctor. The EKG is the "signature" of your heart and many of us may have small abnormalities without necessarily having a disease.