what is the number of orbitals (energy levels) for the element Thallium?

Answer 1

Thallium is element #81 and is in the 6th row of the periodic table. That means its highest energy level is level #6.
However, your question is confusing since orbitals are not the same as energy levels. Each energy level is sub-divided into orbitals which have letter designations of s,p,d,f. If you write the electron configuration for thallium and include the orbitals you would write all of the orbitals involved. That would be:

1s2, 2s2, 2p6, 3s2, 3p6, 4s2, 3d10, 4p6, 5s2, 4d10, 5p6, 6s2, 4f14, 5d10, 6px1