the sims 3 expansion pack "could not verify the integrity of the installer"?

hi so i just installed the sims 3 base game (not the complete game) i download the expansion packs seperately. i followed the instructions and i have the sims 3 base game install but when i try to apply the expansion pack (first i install the late night) as in the ultimate fix, i can't find the "the sims 3: late night folder" on application/thesims3...when i install the late night too a window pop up it says "could not verify the integrity of the installer".
can someone help me pls:/ i dont know what to do.. thank you!

ps: i just found out when i open the base game it says i have to reinstall the base game. i replace the crack files as in the ultimate fix also