Hi Vikas,
As i understanding, you want add leading zero to p_matnr? If yes, you could using FM'CONVERSION_EXIT_MATN1_INPUT' to do this.
CALL FUNCTION 'CONVERSION_EXIT_MATN1_INPUT'
EXPORTING input = p_matnr
IMPORTING output = p_matnr.
select matnr audat auart from matnr into corresponding fields of table lt_mara where matnr = p_matnr.
Regards,
Archer