LYNN – The Lynnway Mart is expanding into the former Building 19 store and preparing for a grand opening of the business in March.Owner Patrick McGrath said the combined retail space will accommodate approximately 150 small businesses. “It’ll be 150 little stores under one roof. They’ll all be selling new merchandise inside the mall,” he said, explaining that the outdoor flea market in the parking lot will continue to operate year round on Saturdays and Sundays.The Lynnway Mart will be closed on Mondays and Tuesdays.”Space is still available, but people are starting to come in to pick out where they want to be located in the building,” McGrath said.Once leased, it will be among New England’s largest indoor malls, with over three acres of rental space.”Whether it’s a space in our existing building or a customized build-it in our newly-expanded building, we’re sure your business will prosper from our location, amenities, advertising and free parking,” he said Monday. “We should be open in 2-3 weeks.”Anyone interested can contact the Lynnway Mart, 800-810 Lynnway on Route 1A north, at (781) 598-5450. It is open Wednesday through Saturday from 10 a.m. to 7 p.m. and Sunday from 10 a.m. to 6 p.m. More information is also available online at www.lynnwaymart.com.