Oracle 21c

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ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';
CREATE TABLE table_name (value) AS
SELECT 'FM73457 2038' FROM DUAL;
1 rows affected

SELECT REGEXP_REPLACE(value, '^(.*) \d\d(\d\d)$', '\2\1') AS replaced
FROM   table_name;

REPLACED

38FM73457

SELECT SUBSTR(value, -2) || SUBSTR(value, 1, 7) AS replaced
FROM   table_name

REPLACED

38FM73457

SELECT SUBSTR(value, -2) || SUBSTR(value, 1, LENGTH(value) - 5) AS replaced
FROM   table_name

REPLACED

38FM73457

SELECT SUBSTR(value, -2) || SUBSTR(value, 1, INSTR(value, ' ') - 1) AS replaced
FROM   table_name

REPLACED

38FM73457