Hey shivani!

If there is N (Capital n) then it is the abbreviation of Newton and newton is the unit used to measure force.

But as you are mentioning that it is in vector chapter , so it can either be newton or if it is not N but a small n with a hat , then it is a unit vector perpendicular to two directions.

But most probably , it is 4 N  means 4 newton which means that four newton units are used to move anything or to bring anything to force.

Hope i have resolved your query!