How long do pawnshops keep paperwork after pawning jewelry?

The answer would depend on the State that the Pawnshop does business.

Most States have a regulatory office for overseeing Pawnshops to make sure that they abide by State Laws.

In MS it is the Department of Banking and Consumer Finance, the same office that regulates Banks since we're also considered financial offices.

I'm assuming that your question is due to a disagreement as to what was used as collateral for a loan.

Also most states have State Associations where you could call to get specific answers to requirements for Pawnbrokers in that State.

Hope that this helps point you in the right direction to get your final answer.