Hooke's law states that for a helical spring the extension is directly proportional to the force applied provided the elastic limit is not exceeded.
Therefore; F= ke, where k is the spring constant, F is the force and e is the extension.
k = 2700 N/m and e = 3 cm or 0.03 M
therefore, F = 2700 × 0.03
= 81 N
Thus, the force required will be 81 N