Install 4x M8 washes onto hobbed bolt then a 608 bearing.
Once installed, does the hobbing on the bolt line up with the small hole going thru the extruder body?
If you need to adjust it's location, you can add either a 0.50mm or 1.0mm shim washer to get the correct spacing.
Holding the motor in the location where it will be mounted, align the herringbone gears by sliding the small gear in or out on the motor shaft so the V-grooves are centered on each other.
Install motor using 3x M3 x 12mm SHCS and 3x M3 washers, taking note of the orientation of the motor wires.
Push the gears together while you tighten the bolts to make sure the contact is tight.
Tighten the set screw on the small herring bone gear.