SQL CONVERT Function

Syntax 
CONVERT(data_type(length),expression,style)

SQL Query
UPDATE HS_HR_EMPLOYEE
SET EMP_EPF_NUMBER = CONVERT (VARCHAR (20),CONVERT(NUMERIC,NSSF_NUMBER))
FROM AAA_NSSF_NO_UPLOAD
WHERE HS_HR_EMPLOYEE.EMP_NUMBER = AAA_NSSF_NO_UPLOAD.EMP_NUMBER