Complex sentence: The largest single building shopping centre in Atlantic Canada by floor space (also the largest single-story mall east of Montreal) opened in 1974 and currently has over 150 stores and services with five anchor tenants.
Split into simpler sentences: The largest single building shopping centre in Atlantic Canada by floor space (also the largest single-story mall east of Montreal). The Mall, as it is referred to, opened in 1974 and has over 150 stores and services with five anchor tenants.