I would try one of the bulbs, and run it at a very low voltage. If you have a meter, try it first at 1 volt, just in case it's really a low-voltage bulb. If you don't have a meter, put it on the DC side of your power pack, the same terminals that your trains run off. Then slowly bring up the voltage. If the bulb comes on right away and is reasonably bright, then it's probably a 1.5 or 3 volt bulb. If it doesn't come on until halfway up the scale, or is very dim until that point, then you've got a 12 or 16 volt bulb. If you run one of the low-voltage bulbs at 12 volts, it's going to pop almost right away.
Even so, I'd run 12 or 16 volt bulbs at around 10 volts. That's my "house wiring" voltage for all of my layout illumination. The bulbs glow with a warmer, more yellow color, and they will last a lot longer. I really don't need the extra brightness I'd get running them at full voltage.
Think about how you place the bulbs inside structures. You don't want to actually see the bulbs through the windows, so consider mounting the bulbs up higher. You can either mount them to the structure roof, or mount them on the layout base on some sort of support. I prefer to mount my bulbs on the base, so that I can remove the structure without disconnecting the bulb.
Another thing you'll notice is that you will see the inside of the building when the lights are on and the room is dark. If the building has large windows, you can think about putting some details inside, like floors, store shelves, etc. I do this by printing stuff from my computer on card stock material and pasting it down inside the building.
Do be aware that even at reduced voltage, incandescent bulbs still give off enough heat to melt plastic. Don't have the bulb in direct contact with the walls or roof. Unless the structure is very, very small, you probably don't have to worry about ventilation, though.
It takes an iron man to play with a toy iron horse.
The ac outputs on your power packs can vary in voltage. I've got one that reads as high as 18v AC. Check yours with a multi meter if you can. Many people use resistors to step the voltage down a bit so the bulbs last longer. If your not putting that many lights in, your power pack will work. If your talking about lighting a whole town then you should think about a separate power supply. Some use old computer power supplies. Some use those 12v wall adapters like you power a CD player with. What you use is gonna depend on how many Ma your drawing. AC or DC will work with those bulbs.