The Museum of Modern Art attracted its highest-ever number of visitors, 3.09 million, during its 2010 fiscal year, according to estimates released Monday by the museum. (The tally is an estimate because the museum’s fiscal year does not end until June 30.) The figure represents an increase of 250,000 over the previous year’s attendance, and a 530,000 increase over the museum’s first full year of operation in its new building (fiscal year 2006).