In the story a group of people needs to bring down a huge alien skyscraper (I have intended it to be around two (2) miles high but I can modify this based on the answers). Note that the alien skyscraper is on Earth and that the people in question have military training (knowledge how to construct a bomb, how to operate bombs) but don't have nor access, nor time to acquire firepower in the range of nuclear weapons and such.
I also had in mind that they would combine many types of bombs to bring down the skyscraper like shockwave demolition bombs as well as thermite: as to ensure that the alien software in the said building (which contains important data collection for aliens) is completely destroyed. It doesn't have to be controlled demolition so the whole thing comes down pretty, it is actually better that it comes down in a chaotic manner, but fall down it must.
How would a stealth bomb squad place those bombs and thermite to ensure buildings destruction and how much explosives would be needed (given that an alien buildings are enhanced and hard to bring down) to achieve this goal?