What blood group/type what blood group/type should not marry in order to avoid having a baby with sickle cell? I am planning to marry and both my fiance and I seem not to know anything about this subject. We would like to know because we both want child

See below. The blood type is not the problem. If you have the sickle cell trait, you need to avoid anyone else with the same trait. A simple blood test should help you with this if you ask your doctor.
This . This is a very straightforward question to answer. If neither of you have any family history of sickle cell anemia or sickle cell trait, it is unlikely that either of you have the genetic capability of having a baby with sickle cell anemia. However, the only way to be 100% sure is a simple blood test called a hemoglobin electrophoresis. If you both have one done and at least one of you has neither sickle cell anemia (which you would already know) or sickle cell trait (which may not be obvious) there is no way that you can conceive a child with sickle cell anemia.