Family Tree DNA (FTDNA.COM) gives the most comprehensive and scientifically based tests. Their web site is explanatory. They have a huge number of people already tested, which means that they can when possible find DNA matches for you from layers of DNA relationships, such as immediate & close relatives way out to fifth and distant cousins. The site provides DNA data and ways to contact people with whom a person being tested shares DNA. The "Family Finder" test is the most satisfying because you receive both male and female findings.
ftdna.com found for me 3 relatives who were/are Jewish from Lithuania in the region of Vilnius and Vitebsk, and those led me to some in Warsaw. Of those who escaped to Canada and USA from European pogroms, I met three people from one family. The two elders (in their early 90s) have passed now, so I was very lucky to meet them. The man of that family looked like my father in profile especially around the mouth, chin, and neck. They welcomed me into their known family to the extent possible. (My father didn't know any relatives of his on his father's side existed.)
I wish you good luck and happy findings!!