Question about tax basis of security [USA]

I owned a bond in a bankrupt company (NINE Energy Services). They recently did a quick bankruptcy and turned my bond into some number of shares of common stock. (It's not what I wanted, but, I have no choice in the matter.) I bought the bond in November 2025

Here's the question: for tax purposes, does this event mean that I "sold the bond" and "bought the stock" on March 1, 2026? Or is it "the bond turned into a stock which bought in November 2025".

When did my short-term/long-term clock start?