Where?
Per USAAF.net:
Altogether, the 422d NFS flew 1,576 sorties in France and Germany, with official credit for 48 German aircraft destroyed (including 5 V-1s), 5 probably destroyed, and 5 damaged. Its crews also claimed to have damaged or destroyed 448 trucks, 50 locomotives, and 476 railroad cars. Six of the nine American night aces of the war came from the 422d: Pilots Paul A. Smith, Herman E. Ernst, and Eugene D. Axtell and R/Os Robert E. Tierney, Edward H. Kopsel, and Robert F. Graham, each with five kills. A distinguished unit citation testified to the squadron’s success. The 425th NFS tallied 14 more kills (including 4 V-1s), with 1 probable and 2 damaged. These 62 claimed kills pale in comparison before the more than 20,000 aerial victories Americans claimed in the daylight against Germany, but the two night fighter squadrons claimed that 55 percent of their airborne radar contacts resulted in visual contacts and 68 percent of these were shot down. The Black Widows were not always successful, but they could be as deadly as their namesakes.
Seems like the 61 was credited with kills to me...here's a list of all squads using the P-61:
Wartime units using the P-61 included:
6th Night Fighter Squadron, Seventh Air Force. Received Black Widows in May 1944. Served in Guadalcanal, New Guinea, Saipan, Iwo Jima. Inactivated February 1947 and reactivated as 339th All Weather Squadron.
414th Night Fighter Squadron, Twelfth Air Force. Received Black Widows in December 1944. Served in Algeria, Sardinia, Corsica, Italy, plus detachment to Belgium. Inactivated August 1947 and reformed as 319th All Weather Squadron.
415th Night Fighter Squadron, Twelfth Air Force. Received Black Widow in March 1945. Served in Italy, Corsica, France, Germany. Inactived September 1947.
416th Night Fighter Squadron, Twelfth Air Force. Received Black Widow in June 1945. Served in Italy, Corsica, France, Germany. Inactived November 1946 and redesignated 2nd Fighter Squadron (All Weather).
417th Night Fighter Squadron, Twelfth Air Force. Received Black Widow in April/May 1945. Served in Italy, Corsica, France, Germany. Inactived November 1946.
418th Night Fighter Squadron, Fifth Air Force. Received Black Widow in September 1944. Served in New Guinea, Philippines. Inactivated February 1947 but reactivated August 1948 as 4th All Weather Squadron.
419th Night Fighter Squadron, Thirteenth Air Force. Received Black Widow in May 1944. Served in New Guinea, Philippines. Inactivated February 1947.
421st Night Fighter Squadron, Fifth Air Force. Received Black Widow June 1944. Served in New Guinea, Philippines. Inactivated February 1947. Reactivated august 1948 as 68th All Weather Squadron.
422nd Night Fighter Squadron, Ninth Air Force. Received Black Widow May 1944. Served in England, France, Belgium, Germany. Inactivated September 1945.
425th Night Fighter Squadron, Ninth Air Force. Served in England, France, and Germany. Inactivated August 1947.
426th Night Fighter Squadron, Fourteenth Air Force. Received Black Widow September 1944. Served in India, China to protect B-29 bases from attack. Inactivated November 1945.
427th Night Fighter Squadron. Served briefly in Italy then moved to India, Burma, China. Received Black Widow in August 1944. Inactivated October 1945.
547th Night Fighter Squadron, Fifth Air Force. Activated March 1944 with P-61. Served in New Guinea, Philippines, Ie Shima, Japan. Inactivated February 1946.
548th Night Fighter Squadron, Seventh Air Force. Activated April 1944 with P-61. Served in Saipan, Iwo Jima, Ie Shima. Inactivated December 1945. Reactivated in 1969 as the 548th Combat Training Squadron. Still in service.
549th Night Fighter Squadron, Seventh Air Force. Activated May 1944 with P-61. Served on Saipan, Iwo Jima. Inactivated February 1946.
550th Night Fighter Squadron. Activated June 1944. Received first Black Widows January 1945. Served in New Guinea, Philippines. Inactivated January 1946.