Custom Module Migration

We migrated 3.7 to 6.2 version . When migrating the custom modules using the 3.7 dll to 6.2, We are not able to find the exact objects and methods in Telerik.Framework. we are facing the following issues 

The type or namespace name 'ManagerBase' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'Web' does not exist in the namespace 'Telerik' (are you missing an assembly reference?)
The type or namespace name 'Cms' does not exist in the namespace 'Telerik' (are you missing an assembly reference?)
The type or namespace name 'WebModule' does not exist in the namespace 'Telerik' (are you missing an assembly reference?)
The type or namespace name 'IToolboxItem' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'Framework' does not exist in the namespace 'Telerik' (are you missing an assembly reference?)
The type or namespace name 'ManagerBase' could not be found (are you missing a using directive or an assembly reference?)
The type or namespace name 'Cms' does not exist in the namespace 'Telerik' (are you missing an assembly reference?)
The type or namespace name 'IControlPanelCommand' could not be found (are you missing a using directive or an assembly reference?)

Please help us in fixing these issues

Hello Aruna,

The reason for your issues is that since Sitefinity 4.0 the API is almost completely changed and to solve your problem, you need to refactor your custom modules. I could advise you to check our Developers Guide tutorial:
http://www.sitefinity.com/documentation/documentationarticles/developers-guide

Hope this information helps.

Regards,
Vassil Vassilev
Telerik