Lewandowski struck in each half on Monday night at the Al Rayyan Stadium to eliminate the African champions Al-Ahly.
"Winning the final at the Club World Cup would be the cherry on top," said the 32-year-old Poland international. “With all the titles we have won ... and then win this additional one.”
Victory on Thursday against the Concacaf champions would enable Bayern to emulate Barcelona who claimed La Liga, the Copa del Rey, Uefa Champions League, European Super Cup, the Spanish Super Cup and the Club World Cup in 2009.
Goal
“At first you don't think that much of it,” added Lewandowski. “But at the end when you know only one team has won six titles in a season and you have the chance to be the second team."
Bayern romped to the 2020 Bundesliga title in July and then completed a domestic double by crushing Bayer Leverkusen 4-2 in the DFB Pokal final.
They powered through the reconfigured Champions League tournament in Portugal with an 8-2 demolition of Barcelona in the quarter-final and a 3-0 waltz past Lyon in the semis.
They claimed the title after a 1-0 win over Paris Saint-Germain.
The German Super Cup and the European Super Cup have also been added to the Bavarians' bulging trophy cabinet.
Glory
"The title at the Club World Cup would be the cherry on top," said Lewandowski. "We can write history but it is also a big challenge. When you are that close to a title then you want to win it.
Bayern arrived in Qatar after beating Hertha Berlin 1-0 in the Bundesliga.
After the final at the Education City Stadium in Al Rayyan, they return to domestic duties with a game on 15 February against Arminia Bielefeld.
