[BenjaminJapan]

To answer your original question, because I'm not sure anyway did, 持つ is the plain dictionary form. This is the most basic form of the verb.

Verbs before んだ take casual form, so that could be 持つ、持った、持たない、持たなかった、持っている、 持っていた、持っていない、持っていなかった、etc.

There's a lot you can learn from anime that you can't learn from novels or textbooks, and there's a lot to learn in novels and textbooks that you'll never learn in anime. The point is that you understand the difference between anime Japanese, casual Japanese, polite Japanese, and extra-polite Japanese. I wouldn't recommend ever trying to speak the first one.