If an atom has an atomic number of 6 and and abdomens mass of 12 how many electrons does it have

Atomic number refers to the proton number of the atom itself. Number of electrons in an atom (an atom that is not reacted with any other molecules / Just the atom alone), is the same as the number of protons, because each electron has 1 negative charge, and each proton 1 positive charge, where they cancel out on each other to become a neutral charge.

So, when atomic number is 6, proton number is also 6, and number of electrons will also be 6 in that atom.

Hope this helps! :)