reading the book of acts 5 to 9, the testimony of Stephen about Abraham, where are they in Genesis?

I'm not going to look it up, but you seem to be thinking that the Old Testament is a complete and thorough compilation of all Judaic writings and tablets before Jesus. I assure you, it is not. Many of the Jewish writings have been lost. In fact, most writings from that time period have been lost. 

See: the cross-references (bottom of page)

https://www.biblegateway.com/passage/?search=Acts%...

It's not just Genesis that Stephen was referring to

but

almost everything he said about Abraham is found in Genesis

and so

I wonder which ***particular*** statements you consider to be "not really in our version of Genesis".

Consider the benefits of Jesus' teachings and clarifications on matters such as those.

Oh... oh  my. Do you mean to tell me that you have found an inconsistency in the Bible? Color me shocked!