I'm assuming you're referring to the Indian film "Mission Majnu" and its availability on a platform called 123mkv. Here's some general information about the movie:

In sum, the weird concatenation of “Mission Majnu 123mkv” captures a moment where cinematic myth-making, digital distribution, ethical ambiguity, and shifting audience practices intersect. It invites us to think about how we consume stories, who controls them, and how the mediums of transmission transform meaning. Behind the file name is a story of production and a parallel story of dissemination—both are essential to understanding how narratives function today.

As you've mentioned "123mkv", I assume you're looking for a way to stream or download the film. However, I must advise that downloading or streaming copyrighted content from unauthorized sources is against the law and can harm the film industry.

The movie is inspired by a true story and revolves around an Indian RAW agent named Kabir (played by Ranbir Kapoor), who goes undercover to gather intelligence on Pakistan's nuclear program. The film follows his mission, codenamed "Majnu," and the challenges he faces.