The stat block for the orc (MM, 246) includes two weapon attacks; Greataxe and Javelin.
For the greataxe, it makes sense that they'd be able to use it repeatedly, and if they were to use their javelin to make melee attacks, then again, it would make sense that they'd be able to use it repeatedly. However, they can also make a ranged attack with the javelin using its Thrown property.
If the orc throws a javelin, the orc no longer has that javelin on their person. Their stat block lists Javelin as an option, so clearly they have at least one (usually, unless the DM decides this orc doesn't, such as if it's a slave or prisoner or something), but how many javelins do they have in total?
Going by the starting equipment of, say, the Paladin (PHB, p. 84) or the Barbarian (PHB, p. 48), it seems reasonable that they'd have a few, but it isn't explicitly stated in the orc's statblock how many javelins they have.
So how many do they have? Are there some general rules about monsters and ammunition that I'm overlooking, or is it up to the DM to decide how many javelins would make sense for any given orc?