If you are doing a migration rather than an in-place upgrade, you will want to get a solution from our support team for your new 2013 organization. Install that solution in the new 2013 environment, and then you will have the entities in place so you can migrate your data. (For your own customizations, you will not be able to export a 2011 version of your customizations and import this into a 2013 environment - the two versions are incompatible. So for your own customizations you will need to upgrade a copy of your CRM 2011 org to CRM 2013, then export your customizations so you have them available to import into your new 2013 environment.)
Note: When you export customizations from any org, you may see a screen that says the solution you are exporting is missing required components and which refers to some ClickDimensions entities - you don't need to worry about this though, because if you have installed our 2013 solution in your environment, you won't in fact be missing them since they will already be in place.