what do i do for my prunus tree the bark split its 30 yrs old

This sort of thing can be caused by something hitting the tree, but it is more likely to have been caused by frost. I'm not aware of anything you can do really - you can't just 'fix' this sort of damage. I'm guessing this is an ornamental cherry - they are in fact considered to be fairly short-lived trees. This wound will allow water in and eventually the wood will rot, but the tree will probably continue to survive for quite a number of years. So it's up to you whether you want to get rid now and plant a new one or keep this one for the timebeing.

Thanks Sid,was worried about the tree ,I will leave it be.