So you want a numeric variable that contains YYYYMM in which case this will do it:
data have;
input month year ;
datalines;
05 2021
04 2020
03 2019
;
data want ;
set have;
want=year*100+month ;
put year= month= want= ;
run;
Although I would recommend you convert your numeric month/year into a SAS Date value and then format that, as follows:
data have;
input month year ;
datalines;
05 2021
04 2020
03 2019
;
data want ;
set have;
sasDate=mdy(month,01,year) ;
want=putn(sasDate,"yymmn6.") ;
put year= month= sasDate= want= ;
run;