To get a force in units of newton you need to express -7.4uC as C, then do the multiplication. Giving the answer using scientific notation is probably the simplest way of giving it.

With the cancellation of powers of 10, it'll actually just be F = -7.4 x 0.281 N = ......

You should be able to the multiplication on paper -without a calculator

And you do realise that you 'lose' the minus once you give the direction ....?