FORECLOSED HOUSE with ILLEGAL SETTLER

my uncle bought a foreclosed house at the NHMFC last year, an illegal settler is occupying the foreclosed house, illegal because they are not the owner, the original owner is nowhere to be found. So after the whole process at the NHMFC of purchasing the foreclosed house finally after one year of grace period given to the original owner to redeem the house is finally over, but then the illegal settler dont want to vacate the house. What is the cheapest way / the best way to do in order to have this illegal settler off my uncles property. He bought a house so they could have one, but then somebody there whose not paying any cents living there doesnt want to leave while my uncle who is now the rightful owner is renting an apartment...its so unfair...
please advice as to what is the best way to do...how much will it cost to secure a notice to vacate? where to get it?....

file a motion in court for writ of possession.