"Impulse" is (force applied) x (time that the force lasts) .
[Force] x [time] units are [Newton] x [second] .
If you go a little farther, it turns out that 'impulse' directly
produces a change in momentum, so it should have the
same units as momentum ... [mass] x [speed] .
In fact, it does ! But I doubt that you want me to go into that
right now, since you really didn't ask about it. So you'll just
have to take my word for it: Impulse and momentum both have
the same units.