Kowloon is a large part of Hong Kong, and Mongkok is small part of it. If you mean you are staying Tsim Sha Tsui, or Kowloon mtr station area, it is not far from Mongkok, about two stops by metro. Yau Ma Tei, Tsim Sha Tsui and Mongkok areas are the shopping center in Kowloon. So, you can easy find malls and shops here. The lady's Street, Mongkok computer street and temple street are all in this area.