The state Department of Labor reported Thursday that Buffalo picked up 3,100 jobs in the private sector in March compared to a year ago, an increase of 0.7 percent. That accounted for one-quarter of the private-sector jobs gained in the 52 counties in Upstate New York — 12,100, up 0.5 percent. The Buffalo Niagara market added an overall 3,200 nonfarm jobs, which accounts for the public and private sectors. Rochester had private-sector job growth of 2,900, or 0.7 percent, in the year-over-year…