The ANA code of ethics is what you are looking for and you can view it, I believe on the ANA website - I think it's nursingworld.com.
It's not going to give you a number value of how many patients you should be caring for.
1. I doubt there is any "ethical rulebook" anywhere that says "no nurse shalt have more then 6 patients per shift".
2. Someone else will probably point this out - but the ANA represents RNs. Leaves LPNs/LVNs rather out of the picture. Do we have separate set of ethics?
3. Each State/licensing authority has different "policy" and "responsibilities" expected by the licensee. This will obviously affect "ethics".
4. The question asked by the OP is too vague to merit a precise answer.