How to migrate Files and images from Episerver 6 R2 to Episerver 7.0.586.1 (version less than 7.5)

Hi,

I am trying to migrate files and images from episerver 6 r2 to Episerver 7.0.586 , via Migration tool , but getting the error as below

Object reference not set to an instance of an object.

at VppMigrationTool.Util.SiteProxy.InitalizeEPiServer(String webConfigPath) in e:\Sotwares\vppmigration-source-code\VPPMigration\VppMigrationTool\Util\SiteProxy.cs:line 45
at VppMigrationTool.Util.SiteProxy.Initialize(String destinationPath, String virtualDirectory) in e:\Sotwares\vppmigration-source-code\VPPMigration\VppMigrationTool\Util\SiteProxy.cs:line 129
at VppMigrationTool.Util.SiteProxy.Initialize(String destinationPath, String virtualDirectory)
at VppMigrationTool.Converter.get_RuntimeProxyWrapper() in e:\Sotwares\vppmigration-source-code\VPPMigration\VppMigrationTool\Converter.cs:line 52
at VppMigrationTool.Converter.FillSiteData() in e:\Sotwares\vppmigration-source-code\VPPMigration\VppMigrationTool\Converter.cs:line 101