The Wielding Items section of the rules (CRB 272) covers this. Table 6-2: Changing Equipment states that drawing a weapon takes an Interact action in its first entry:
Photo credit to Archives of Nethys.
Consider a dual-wielding character with two weapons. Each weapon is one item, and so it would take 2 separate Interact actions to draw both items. The Quick Draw level 2 class feat available to Rangers and Rogues allows you to Interact to draw a readied weapon and Strike with the same action, and the first level Alchemist feat Quick Bomber similarly allows you to draw a readied bomb and Strike with one action.
A readied weapon or item is one that is not currently held or wielded but is stored in an easy-to-reach holder, such as a bandolier for alchemical bombs or a sheathe for a sword. If your weapon is instead in a backpack or other container that you cannot quickly draw from, you must spend an Interact action to first open or ready the container (such as taking off your backpack) and then another action to draw the item.