LOL
Just pick up a 15' 16/3 extention cord cut the female end off for $8 and solder black on the brown wire side and white on the blue side of the filter and obviously green to the center ground lug.
Just do it right the cords are 20-30 years old is it worth burning your house down or shocking someone over?

The original bally cords are polarized it why one side of the jacket is rough with raised lines and the side is smooth thats how they determined polarity on these on older molded cords you will even see it on current day molded cords on side will have a texture side and a smooth side or one side will have a white line or printing to show its polarity.
the smooth side signifies black/hot
The textured or lined side signifies white/neutral
And in a 3 conductor wire the center is green/ground

White should goto the blue side and black should goto the brown side of the RF filter the in/out run parallel
Just becouse it came this way from the factory dont meen it was hooked up properly to begin with.