Should i create a third class and do the job in BLL?
or should i do it in UI using LINQ to Entities after i fetch them?
That would depend on where you need this class. If it is for displaying purposes then it should live in the UI. This class even has a name in this case: it's called a view model and is what your controller action could pass to the view after querying your DAL layer and projecting the various results to this view model.