I have to take random urines for probation and need to know how long it is detectable after last drink

It has a lot to do with amount, body weight and more.

Also which type of test are they using, urine or hair test. And what level of substance will make it fail

But roughly 2 or 3 days.

Also remember that if someone gets mad, and turns ou in, or takes pictures of you out drinking the PO ( assuming PO) can use that also