Are clothes that contained semen and were washed in an automatic washing machine with pure clothes all considered pure, or have they become impure? And what is the ruling on praying in them if they are not pure, given the previous ignorance of this matter?

Human semen is pure, according to the more preponderant opinion, so there is no problem in washing clothes that have semen on them with other clothes. As for washing impure clothes with pure ones in an automatic washing machine, we have clarified what pertains to that in previous fatwas.