Convert And Sql Query To Access

someone wrote this query for me in SQL and there is one part of it I don't understand can someone tell me how to convert this line for access? I don't know what || is

TO_NUMBER(SUBSTR(TO_CHAR(WE.mth_welfare),5,2) ||
SUBSTR(TO_CHAR(WE.mth_welfare),1,4)) an_mth_welfare


SELECT
WE.mth_welfare,
WE.id_case_welfare,
WE.id_case,
OB.id_member,
SUM(WE.amt_mtd_assist_expnd),
SUM(WE.amt_ltd_assist_expnd),
SUM(WE.amt_ltd_assist_recoup),
TO_NUMBER(SUBSTR(TO_CHAR(WE.mth_welfare),5,2) ||
SUBSTR(TO_CHAR(WE.mth_welfare),1,4)) an_mth_welfare
FROM noldba.welfare_balance_by_obligation WE, noldba.obligation OB
WHERE WE.id_case = OB.id_case
AND WE.seq_order = OB.seq_order
AND WE.seq_obligation = OB.seq_obligation

AND WE.mth_welfare <= 200708
AND WE.dt_END_validity = '31-DEC-9999'
AND WE.dt_end_validity = OB.dt_end_validity
AND OB.dt_beg_obligation = (SELECT MAX(c.dt_beg_obligation)
FROM noldba.obligation c
WHERE c.id_case = ob.id_Case
AND c.seq_order = ob.seq_order
AND c.seq_obligation = ob.seq_obligation
AND c.dt_end_validity = '31-DEC-9999')
GROUP BY WE.id_Case, OB.id_member, WE.id_case_welfare, WE.mth_welfare
ORDER BY WE.mth_welfare DESC,
WE.id_case DESC,
OB.id_member DESC;