My probation ends tomorrow, I go on Monday to pick up my papers, can they drug test a day after my probation done...

Your probation ends officially on the day it is signed off. It is not uncommon to be tested right before your release

...i go on monday to pick up my papers,...

What "papers" are those?

My po said Monday I just take 5 minutes to sign some papers and be done... I just want to drink a couple beer's, don't want to get screwed by an EtG though, just wondering if they could legally ask me to take a test on the day after my court orderd probation ends, or if they can...

Those papers are ending your probation , you are not off till those are signed ( and then normally signed by the judge) and yes at this "meeting" it is common for some PO to test