For each password character, there are 26+26+10=62 possibilities. That brings the total number of possible passwords to 62⁶ if we wouldn't consider the additional constraints.
- No passwords without numbers allowed, so we subtract 52⁶
- No passwords without uppercase allowed, so we subtract 36⁶
- No passwords without lowercase allowed, so we subtract 36⁶
Now we have subtracted the passwords of all capitals twice, so we have to add those back in: add 26⁶
Same for all lowercase and all numbers: add 26⁶ and 10⁶
end result: 62⁶ -52⁶-36⁶-36⁶ + 26⁶+26⁶+10⁶ = 33294892800