i am totally confused. your alternator doesnt have a tensioner pulley.
you have the alternator pulley, lower bracket and upper bracket. To tension it, you mus loosen the upper and lower bolt and the alternator will pivot on your lower bolt thus sliding the upper bolt back to tighten tension.

They are cheap from the dealer btw. you need a special bolt for the top with a hook and its 8x1.25 thread with a 12mm nut. and the bottom is a special square head bolt with a 10x1.25 with a 14mm nut