which sentence is correct I served him for two good years or I served him for good two years?

Adjectives of number always come first, so it's "two good years." There is an order in which multiple adjectives are listed in English, which most native speakers know without having studied it. (However "I served him for a good two years" is an expression meaning somewhat more than two. Similar example: "I've been waiting a good ten minutes for you to show up.")

Quantity or number
Quality or opinion
Size
Age
Shape
Color
Proper adjective (often nationality, other place of origin, or material)
Purpose or qualifier

two good years

I served him for two good years is correct

1