I need to find a web site for free info on what legal rights a parent who has been in prison has to their child and how I need to go about gaining sole custody of my child to keep her convict father from having any custody.

Merely going to prison, does not automatically take away any of a fathers rights. You will have to show the court evidence of why he should no longer have any rights.

You will need to hire an attoreny or get one though a legal aids socieity.
You will have to file for divorce if you are married to him, and file for custody of the child.

HI,
The answer before mine said get a lawyer. I agree with the fact that you do need a lawyer. You can go to the Court House in your local area, go to the Court Clerk's Office, and they might be able to guide you to a "free" legal aid lawyer, if you can't afford to pay one.
Best of luck.