There are 2 towns with "Naumiestis" in it, one called Kudirkos Naumiestis in the S^akiai district and the other, Z^emaic^iu Naumiestis in the S^ilute district.
Since there are no listings for any surname beginning "Pociu-" in the online phone book for Lithuania in Kudirkos Naumiestis, but several in Z^emaic^iu Naumiestis, it seems likely that the latter is the correct "Naumiestis."
Here are the listings for people with the surname, Pocius (Pociute for unmarried women, and Pociene women married to a Pocius). It seems likely that some of these are related to your friend:
Adolfas Pocius
Bikavenu k.
Vainuto sen.
S^ilutes raj.
844149570
Alfonsas Pocius
Pas^ys^iu k.
Juknaic^iu sen.
S^ilutes raj.
844145747
Algirdas Pocius
Lauc^iu k.
S^ilutes sen.
S^ilutes raj.
844145492
Algis Pocius
Bliudsukiu k.
Gardamo sen.
S^ilutes raj.
844169001
Aretas Pocius
Pievu g. 12
S^ilutes sen.
S^ilutes m.
844177425
Bronius Pocius
Juknaic^iu k.
Juknaic^iu sen.
S^ilutes raj.
844158634
Edmundas Pocius
Vainuto mstl.
Vainuto sen.
S^ilutes raj.
844144187
Giedrius Pocius
Vilkyc^iu k.
Saugu sen.
S^ilutes raj.
844144641
Gintaras Pocius
Pas^ys^iu k.
Juknaic^iu sen.
S^ilutes raj.
844145739
Jonas Pocius
Katyc^iu mstl.
Katyc^iu sen.
S^ilutes raj.
844141619
Jonas Pocius
H. S^ojaus g. 2a-4
S^ilutes sen.
S^ilutes m.
844176060
Jonas Pocius
Cintjonis^kiu g. 2-202
S^ilutes sen.
S^ilutes m.
844154779
Juozas Pocius
Melioratoriu kv. 6-39
S^ilutes sen.
S^ilutes m.
844154740
Kestutis Pocius
Kurs^mariu g. 6
Rusnes sen.
Rusnes mstl.
844158597
Povilas Pocius
Knygnes^iu g. 17-26
S^ilutes sen.
S^ilutes m.
844176221
Povilas Pocius
Cintjonis^kiu g. 12-12
S^ilutes sen.
S^ilutes m.
844151018
Romualdas Pocius
Jonaic^iu k.
S^ilutes sen.
S^ilutes raj.
844145441
Stasys Pocius
Dariaus ir Gireno g. 5-201
S^ilutes sen.
S^ilutes m.
844176137
Tadas Pocius
Jaunimo kv. 8-18
S^ilutes sen.
S^ilutes m.
844175282
Tomas Pocius
Liepu g. 19-14
S^ilutes sen.
S^ilutes m.
844162434
Aldona Pociene
Juknaic^iu k.
Juknaic^iu sen.
S^ilutes raj.
844158859
Dana Pociene
S^iloko g. 6-12
Juknaic^iu k.
Juknaic^iu sen.
S^ilutes raj.
844157458
Donata Pociene
Laisves kv. 1-24
S^ilutes sen.
S^ilutes m.
844151029
Elzbieta Vanda Pociene
Pas^ys^ kiu k.
Juknaic^iu sen.
S^ilutes raj.
844145772
Genovaite Pociene
Gluosniu g. 5-4
S^ilutes sen.
S^ilutes m.
844151766
Irena Pociene
Taikos g. 8a-2
Rusnes sen.
Rusnes mstl.
844158157
Irena Pociene
Sodu g. 12-2
S^ilutes sen.
S^ilutes m.
844177381
Irena Pociene
Vainuto mstl.
Vainuto sen.
S^ilutes raj.
844146885
Janina Pociene
Gluosniu g. 5-23
S^ilutes sen.
S^ilutes m.
844154035
Maryte Pociene
Vainuto mstl.
Vainuto sen.
S^ilutes raj.
844144382
Ona Pociene
Petreliu k.
Saugu sen.
S^ilutes raj.
844146705
Ona Pociene
Taikos g. 3-3
S^ilutes sen.
S^ilutes m.
844153746
Ona Pociene
Stubriu k.
Katyc^iu sen.
S^ilutes raj.
844149225
Renata Pociene
Berz^u g. 1-14
Deguc^iu k.
emaic^iu Naumiesc^io sen.
S^ilutes raj.
844146239
Silva Pociene
Tarvydu k.
Juknaic^iu sen.
S^ilutes raj.
844158612
Stanislava-Birute Pociene
Melioratoriu kv. 11-18
S^ilutes sen.
S^ilutes m.
844152750
Terese Pociene
Skirvytes g. 4
S^ilutes sen.
S^ilutes m.
844176520
Vanda Pociene
S^yliu k.
Gardamo sen.
S^ilutes raj.
844143616
Nijole Pociute
Melioratoriu kv. 9-9
S^ilutes sen.
S^ilutes m.
844175743
The abbreviations used are:
g. = gatve, street
m. = miestas, town
mstl. = miestelis, small town
sen. = seniujia, eldership (sort of a township or borough)
raj. = rajonas, district
The endings of the place names reflect the possessive case (because Lithuanian uses several different case endings.)
Your friend might consider calling these folks (if he speaks Lithuanian) or writing to them either in English (often someone is around who can translate) or in Lithuanian (many folks on this forum will translate simple messages from English to Lithuanian).