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Moz has no access to Google Webmaster Tools, so setting something there wouldn't affect the reports you're getting in Moz.

No problem! Glad to hear you're working on it. I just know that will help your site so very much. Good luck!

There isn't a way to do this in Moz Pro Tools, but I believe there is a way to do this in some of the upgraded (paid) subscriptions for SEMRush. I think even there, there is a limit to how far you can go back. If you changed any of your URLs when you went through your site redesign, you may just need to audit old links, new links and your 301 redirects to make sure all of them are functioning as expected. Ultimately, the rankings that you had are really less important than what your traffic is telling you. It could be that you inadvertently took down some highly linked and highly visited pages, and, regardless of rankings, that's hurting you now. One thing you can do is backtrack in Google Analytics and look to see if you had specific pages that were producing a lot of traffic before that aren't now. That will help you zone in on the problem and fix it.

Yes I am using Magento. I did exactly what you said but I think magento set it up wrong. Please see my other question that I just made listing what went wrong.