Just to add what Brenden said - there was a bug in Import toolkit v11 when selecting page types. It was fixed in hotfix 11.0.5 - " Import toolkit - Error when importing certain object types. When attempting to import certain object types (for example pages) using the Kentico Import Toolkit utility, an error occurred in the source data preview step ("Cannot load default column mappings. Class not found.")."
So, you may need to apply the hotfix at first - use some Kentico 11 instance you have and map the hotfix tool on it. Then, in one of the steps switch to "advanced mode", unselect the project and SQL script options and select the Setup files option to fix the setup file.