Looks like that is the ABS unit, but I may be mistaken, are there brake lines coming off of it that you can see? 200 is probably the right ohms scale, but it wont hurt anything to try other scales depending on what the resistance value. To figure out where you will be testing, you need to trace both of the wires pictured to find where they go. Test the side of the actual sensor, not the ABS unit itself.

You will be testing between either 1&2 or 3&4

It looks to me that the 3&4 side would lead to the sensor itself, but I may not be right because of where the picture is taken. Just follow the sensor wire and test the sensor side, not the ABS unit side.

After taking a resistance check, you will probably want to do a continuity check also. This can be accomplished by setting your multimeter 1 more counterclockwise than it is in the picture. If the sensor is good, you should here a beep when the probes are touched to the ends of the sensor lead.