www.usps.com has a price calculator where you can get your price.

Without knowing size & weight of your item, no one can give you the answers you want. But the USPS site will

Hi, if I were to write to Muhammad Ali would he read it if I sent it to his home address in Arizona? (does he still live in Kentucky?). Or what about Mike Tyson? Also how many global forever usa air mail stamps would I need to include? Thanks