do you still have the instruction manual/care guide that came with your hearing aids? if so, it should be listed there. if not, look at your hearing aids for a letter "r" and "l." the serial number is usually preceeded or followed by these letters.
I found some numbers on the bottom of the carptment where you put in the battery. I am correct in assuming these numbers are the serial number?
Yes, they are either in the battery compartment (not on the door) or along the under side of the aid. Every manufacturer seems to put theirs in a different place and I'm not familure where interton puts theirs. Worst case you can call the manufacturer and they can tell you where to look as well as look them up for you.