I would respectfully disagree with others who are suggesting various opinions of "ask for ???" regarding the salary pay. Even though it's an internal vs external opportunity, I would still focus all of your questions/conversation on the actual job responsibilities, how you can contribute to making it better, etc. and leave the salary discussion to them. If they bring it up during the interview, then obviously you need to be prepared to discuss it... but that's different than you actually asking for a certain salary that you would like them to meet.
Get the offer first!!! Once they offer then you can always counter, if desired, and still have the option to accept the position or not. Most positions have a salary range, so find out where your current salary would fit within the range of the new position and that will give you an idea of the growth potential within that position. Even if the initial offer isn't up to what you may want, the future increases could be significant depending on where you fall within the salary range.