Squash in Egypt

I planted a squash plant that i got from kmart as a seed. Know i do not remember what type it is. how do i tell when to pick it? the squash are green and they had yellow flowers that fell of them. when they die, they turn yello. Know a lot of them are dying. Do i pick them or is it time to pick them
I do not know. It does not look like zuchini.

Is it zuchini?