If your new kitchen is two tiles longer and the same width and you need 10 extra steps, I would conclude that the width is 5 tiles. Trying on a piece of paper shows that only odd lengths work and that any odd length works apart from multiples of 5. I only tried 1, 3, 5, 7, 9. Assuming that the length is longer than the width and that the length is not more than twice the width I would guess your kitchen is 9 tiles long but it could be much longer.