You choose a target creature as Scrounging Bandar's triggered ability is put onto the stack. You choose how many counters to move (if any) as that ability resolves. If that creature becomes an illegal target or if Scrounging Bandar has left the battlefield, you can't move any counters.

To move a counter from one creature to another, the counter is removed from the first creature and put on the second. Any abilities that care about a counter being removed from or placed on a creature will apply.