Using following SQL can get the BU id by BU name

SELECT hao.organization_id as bu_id,haot.name,hao.business_group_id
FROM
HR_ALL_ORGANIZATION_UNITS_F hao,HR_ORGANIZATION_UNITS_F_TL haot
WHERE
hao.ORGANIZATION_ID = haot.ORGANIZATION_ID
AND hao.EFFECTIVE_START_DATE = haot.EFFECTIVE_START_DATE
AND hao.EFFECTIVE_END_DATE = haot.EFFECTIVE_END_DATE
AND TRUNC(SYSDATE) BETWEEN hao.EFFECTIVE_START_DATE
AND hao.EFFECTIVE_END_DATEAND haot.LANGUAGE='US'
AND haot.name like '&BU_NAME%'