# Number of orbitals in full configuration interaction

I am using one quantum chemistry package where I am supposed to assign a number of active orbitals I want to be included in the FCI (full configuration interaction) calculation. For example if I have ${H_2}$ molecule (singlet) and I use $cc-pV6Z$ basis set of Dunning, what would be the maximum number of active orbitals in the FCI? Can somebody provide me insight into this problem?