I'm assuming that you want to covert atmospheres into mmHg.
mmHg is exactly like torr: there are 760 of them in an atmosphere.
The conversion would be 760 mmHg = 1 atm
Knowing this, simply multiply 2.48 * 10^3 by 760:
2.48 * 10^3 * 760 = 1,884,800 mmHg.
But wait! I'm assuming you probably meant to write 2.48 * 10^-3, since 1,884,800 is an awfully big number.
In that case:
2.48 * 10^-3 * 760 = 1.8848 mmHg
-T.B.