Do you mean that you would like to establish the specific town/city/village in Russian Poland from whence they came?
I would first urge you to provide the details (names, ages and location) of the family that you have found in the 1871 census.
The first step would be to try to trace the family through the other censuses up till 1911. If you're lucky, a more specific place of birth may have been recorded in one of the years.
The other thing to investigate would be naturalisation records. You can search for these on the website of the UK's National Archives. The National Archives
Did this family have any children with them, i.e. born in Russian Poland, who then later married in the UK? If this is the case, it will be worthwhile investigating whether a so-called marriage authorisation is held in the archives of either the United Synagogue or the Federation of Synagogues, whose chief rabbis issued such authorisations to permit a couple to marry in a synagogue. The MA should specify the place of birth of both groom and bride. I can provide more details later.