There are only 4 wraiths in the whole level, and one of them is at the very end and there is no scorpion that far into it.
There are 5 in the level (that I know of)
1 is in where you can get the warthog, another in the next major area after you get the scorpion, the 3rd above the entrance to the underground area just after the second wraith (somewhat hard to see and I’ve haven’t seen it fire at me), when the screen shows “Rolling Thunder” (when exiting the underground area), there will be the fourth wraith in the back right of the area.
And the 5th is near the end (hard to miss)
There are actually 5 wraiths. One before you get the scorpion, and four after.
Seriously, how hard would it be to type “wraith hunter” into youtube’s search bar?
Plenty of videos.