What does this message mean by "non-believer" ?

This is a quote, so I apologize for the many spelling and grammatical errors. Please interpret for me; how do these men become believers? "Now let me tell you in brief. Back in the days of Prophet Muhammad (SAW) the followers of our beloved Prophet killed the male non bielevers and had with their wives. Those woman were made slaves are were known as KAFIR which is an arabic term and it means non believer. However a contract was required to clearify that you own the slave and can do whatever you want with the slave until the contract expires. There is no problem to have with slaves because SLAVES are also LEFT HAND POSSESIONS AND YOU OWN THEM. Go to Surat al-Muminun and read verse 5 to 7." Thanks for any help