The universe we live in determines how many dimensions we exist in.

If we live in a ten dimensional universe, we must be 10 dimensional beings. However, the length we would extend into the higher dimensions would be minimal. For example, a 2 dimensional creature residing in a 3 dimensional universe would have a length, width, and if you looked closely a small height. It would be similar to a piece of paper. The length and width of the paper are easily measurable, while the height would be extremely small and not easily measurable. If the paper had only a length, width, and no height, it would not exist in a 3 dimensional universe.

Therefore, if we live in a universe with 10 spatial dimensions, we must be 10 dimensional beings.