This is this actually quite a hard question for M1. Is it really an M1 question? - it wouldn't come up in any M1 exam. The question is easier if you use the scalar product but that doesn't come up until A2.
The moment of the force
F1 about the origin O is the magnitute of
F1 multiplied by the perpendicular distance from the line of action of
F1 to O.
Below I've added some values to my diagram using the vectors given in the question. 'd' is the perpendicular distance that you need to find.
See if you can use trig to find the value of 'd'. Then multiply this by the magnitude of
F1 and you're done. Let me know if you need more help.
I get the answer as 16Nm if you want to check it.
For the sense of the moment, imagine this is a see-saw question where O is the centre of some rod and there's a force
F1 applied from the point A on the rod. Is this an anitclockwise or clockwise moment about O?