The repetition of the word know in Romans 6:3,6 & 9 indicates that Paul wants us to understand a basic doctrine. Christian living depends on Christian learning; duty is always founded on doctrine.
If Satan can keep a Christian ignorant, he can keep him powerless.
The basic truth Paul is teaching is the believer’s identification with Christ in his death, burial and resurrection. Just as we are identified with Adam in sin and condemnation, so we are identified with Christ in righteousness and justification.
At Romans 5:12, Paul makes a transition from discussing sins to discussing sin- from the actions to the principle- from the fruit to the root.
Jesus not only died unto sin and we died with Him.