Hi Tara:
Assuming the hardware did not somehow break (fairly unlikely from just plugging in an external keyboard), perhaps the keyboard “map” got changed somehow.
The most likely situation is that you invoked the number pad “overlay” on your laptop keyboard. Many laptops have a virtual “number pad” often approximately where the “u, i, o, j, k, l, m, “,”, and “.” keys are. This helps with speedier “ten key” numeric entry. [You will probably see a light blue, or perhaps green “overlay” printed with 0-9 on just those keys.]
Your manual can tell you how to turn this on and off (it’s different for each type of laptop — usually accomplished with a hardware switch near or on the keyboard or with a Fn key).
Or this external keyboard somehow changed the way the OS recognized the keyboard. Depending on your OS, there are different ways of doing this. In Windows you should be able to type “keyboard” after invoking the Start menu to see how to change the keyboard type.
Good luck!