Parra, who will battle it out with Maxime Machenaud for a starting spot in France's opening Six Nations game in Italy on February 3, now wants Clermont to finish the job away to the Scarlets, and then build on that to win the competition.
He said: "It's important to maintain the form we've shown in our last games, it's good to build on it, and above all to have a home quarter-final is vital, so we have to finish the job.
"We need a point to be sure of that, but if we just play for that, it's the easiest way to mess it up and concede 30. We will try to produce a big performance in Llanelli and win over there, we can't underestimate them. Even though they've lost all their games, they have some good players and want to end on a high in front of their home crowd.
"If we want to be European champions, we'll have to beat everyone, and that starts with Llanelli. We have to work on how we start games, not conceding early tries as we did against Montpellier. To finish the pool stages unbeaten would be a first for the club, but finishing unbeaten and not becoming European champions is pointless."