Error after upgrading from 6.2.4910.0 to 8.0.5712.0

I'm using the project manager to upgrade my site from  6.2.4910.0 to 8.0.5712.0 and now when I start the site I get the following error: 

Could not load file or assembly 'Telerik.Sitefinity, Version=6.2.4910.0, Culture=neutral, PublicKeyToken=b28c218413bdf563' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)
  Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.
 Exception Details: System.IO.FileLoadException: Could not load file or assembly 'Telerik.Sitefinity, Version=6.2.4910.0, Culture=neutral, PublicKeyToken=b28c218413bdf563' or one of its dependencies. The located assembly's manifest definition does not match the assembly reference. (Exception from HRESULT: 0x80131040)

 Project manager said that it was successful. What's up? How do I fix it?

John,

Take a look at binding redirects in your web.config file.  Take a look at Sitefinity Steve's blog as he has an example of how perform your fix. 

www.sitefinitysteve.com/.../sitefinity-how-to-list Version errors with Assembly Binding​

Here is the code that could help you.  You will have to add this to your web.config.  Hope this helps.