Dec 23 (Reuters) - England captain Joe Root has backed himself to get a first Ashes hundred in Australia as he prepares for the third test starting in Melbourne on Boxing Day, a must-win game if England are to claim the series. Root has already plundered an English record 1,630 test runs in 2021 and has two half-centuries in the Ashes series so far with 89 in Brisbane and 62 in Adelaide as his side slipped to two heavy defeats. He has also seen Australia"s Marnus Labuschagne take over his position as the number one batsman in the world after the second test. "I feel in a really good place with my batting," Root was quoted as saying by Sky Sports. "I feel confident I can, in these next three games, bang out a hundred in these conditions. "I know that"s a brave thing to say but my conversion rate this year, it"s not been an issue at all. "I have an understanding of how I want to score my runs. There"s clarity there, I just need to keep putting myself in those positions, just have the bit between my teeth." Root has yet to score a century in Australia, where he averages under 40, well below his overall test average of 50.01. His 89 earlier in this series is his highest score Down Under. But he also expects a response from the team all round in the Boxing Day (Dec. 26) test, the start of three must-win games. "There is plenty of motivation for the group and we are doing everything we can to make sure it is 2-1 by the time we leave here," Root said. "If we perform anywhere like we can do, we"ll put them (Australia) in an uncomfortable position, we"ll push back and we"ll find ourselves in a very different situation leaving this ground."