Can someone tell the me the data bank which has all the STO-3G basis sets for many electron atoms?
A wide range of Gaussian basis sets for all elements can be found at the Basis Set Exchange. Alternatively, you can try to extract that data from the basis set library of a quantum chemistry software package.
The functional form of a primitive cartesian gaussian with $l=0$ is $\exp(-\alpha r^2)$, independent of the $n$ quantum number.