hello charitha,

as you secured 6600 rank in the JEE MAINS paper-1 so according to your rank and the previous year analysis out around 30 NIT you can easily be a single holder of seat in the rest 15 NITs in the south india side NITs its difficult to get seat in the top branches,

but can hold seat in the northern side NITs easily in the top branches .you try to the sourthern NITs if chance permits you secure seat there