Need advice about chains for 2007 and 2005

Hello there. I live in Nevada where we have big snow occasionally. I bought chains for my car and my daughter's last year without ever trying them or using them last winter. I needed mine today and, although I bought what the Toyota dealer said I should buy and I bought them from him, the chains don't work. The tires rotate inside the chains. I had good help putting the chains on, so I doubt that is the problem.

I am so angry at myself for not taking the time to try out the chains, and at Toyota for giving me the wrong chains, because I have sent my daughter up the mountains many times with the chains I bought her in her car, thinking she had chains so she was OK. What an idiot I was not to try them out!

I intend to go back to the dealer and ask him to exchange them, even though I bought them about a year ago.

Two questions: What chains do I need and is there anything special that has to be done to get them on right for my 2007? Same question for my daughter's 2005?

We get lots of questions about the two Priuses at the house, and we just say we bought them at the two for one sale. Really, I couldn't get any face time with my car when I owned the 2005 because my daughter loved it so much. In 2007 I gave up and let her have it and got another one. Thank goodness I don't have any more kids to take this one.