Answer:
The answer is: I might have forgotten that small town where I went to elementary school only for two years in the late 1960s.
Step-by-step explanation:
In this case, this excerpt includes an adjective clause which is where. It is important to know that adjective or relative clauses have some characteristics that can help to determine when a sentence is containing a clause. Some of these characteristics are: the use of a subject and a verb inside the sentence and; the use of a relative pronoun or a relative adverb. Regarding this sentence, we can analyze that I is the subject, went is the verb and where is the relative adverb. Besides, it is important to mention that an adjective clause works as an adjective since it provides some information about the noun of the sentence. Having said that, the noun of this sentence is small town and the information we have about it is that the subject studied there when he or she was at elemetary school.