Step 1: Concept Identification: The query seeks the Yāska's Nirukta term for verbal/nominal prefixes like \textit{pra} and \textit{pari} that alter meaning.
Step 2: Elaboration: Yāska's Nirukta, Chapter 1, categorizes words into four types (\textit{catvāri padajātāni}):
1. Nāma (Noun/Nominal): Denotes entities or substances.
2. Ākhyāta (Verb): Denotes actions or states of being.
3. Upasarga (Prefix/Preposition): These, such as \textit{pra}, \textit{pari}, \textit{apa}, \textit{sam}, precede verbs or verbal nouns to refine their significance. The description matches this definition precisely. For instance, \textit{hṛ} (to take) transforms into \textit{prahṛ} (to strike) with the addition of the \textit{upasarga} \textit{pra}.
4. Nipāta (Particle): Indeclinable words serving diverse roles like comparison (\textit{iva}) or conjunction (\textit{ca}).
Step 3: Conclusion: The term for elements like \textit{pra} and \textit{pari} in this context is Upasarga. Therefore, option (2) is correct.