The answer is the following: Four (Adj); score (N); and (Conj); seven (Adj); years (N); ago (Adv).
“Four” is an adjective because is giving information about the noun that follows, “score”. “And” is a conjunction. Conjunctions are used mainly to join phrases within a sentence. “Seven” is the adjective that is describing the following noun, “years”. Finally, “ago” is an adverb of time that is used in the simple past tense to indicate the period of time that has passed from the beginning of the action.