Yes those files are only supported under .NET 4
So you need to delete the files it complains about from the /bin folder
ie delete the file Microsoft.Web.Infrastructure.dll
after you delete that the error will change to complain about a different file, there are probably like 5-8 files that it will complain about, just delete each one it complains about and then it should be fine.
Be careful not to delete the wrong files though, note carefully their names in the error message.
Hope that helps,