How many rounds did the event rings: king of kings 2000 block a have with a record of 6-1?
CREATE TABLE "mixed_martial_arts_record" (
  "res" text,
  "record" text,
  "opponent" text,
  "method" text,
  "event" text,
  "round" real,
  "time" text,
  "location" text
);
SELECT "round" FROM "mixed_martial_arts_record" WHERE "event"='rings: king of kings 2000 block a' AND "record"='6-1';