I am getting following errors while exporting a Community Template from Sandbox

Error 1:TileMenu : We can’t validate the page you’re exporting. In field: Network - no CommunityTemplateDefinition named PortalF52 found
Error 2:Default Navigation : We can’t validate the page you’re exporting. In field: Network - no CommunityTemplateDefinition named PortalF52 found
Error 3:TileMenu : We can’t validate the page you’re exporting. In field: Network - no CommunityTemplateDefinition named PortalF52 found
Error 4:PortalF52 : We can’t validate the page you’re exporting. In field: defaultThemeDefinition - no CommunityThemeDefinition named PortalF52 found

Is there is pre-requisites I need to do before exporting a template? 

any help is appreciated. 

Thanks

Create a Visualforce page that uses a custom controller to display a list of cases with the status of 'New'.The page must be named 'NewCaseList'.
The custom controller Apex class must be named 'NewCaseListController'.
The 'NewCaseListController' Apex class must have a publically scoped method named 'getNewCases'.
The 'getNewCases' Apex method should have the return type of 'List' and return a list of case records with the ID and CaseNumber fields and filtered to only have a status of 'New'.
The 'NewCaseList' Visualforce page must use an apex:repeat component which is bound to 'newCases'.
The apex:repeat component must refer to the var attribute as 'case'.
Within the apex:repeat component, bind a apex:outputLink component to the ID of the case so that the page directs the user to the detail page of the respective case record