Table schema:
CREATE TABLE table_name_15 (modern_equivalent VARCHAR, pre_1009_province VARCHAR, province_of_silla VARCHAR)

Question: What kind of Modern equivalent that has a Pre-1009 province of sakbang -do, and a Province of Silla of sakju?
SQL: SELECT modern_equivalent FROM table_name_15 WHERE pre_1009_province = "sakbang -do" AND province_of_silla = "sakju"