Convert a string to a number with a batch fil

Hi,
I'm reading string from a CSV file and I want to convert this string to an Integer (all the strings in the file are numbers' format). I want to write this using batch file.

this a sample of my code :
for /F "tokens=1,2 delims=," %%A in (File1.csv) do (
for /F "tokens=1,2 delims=," %%X in (File2.csv) do (
if %%A == %%X (
set /a R=%%B + %%Y
echo %%A,%%B,%%Y,%R%>>Results.csv )
)
)
My issue here is that R is all the time empty (I guess I can't add 2 strings).

I need help.

Thanks a lot.