The 123mkv part is likely a release group or website tag, not part of the movie title.
The most likely full title is:
(2012) — a Bollywood film directed by Yash Chopra, starring Shah Rukh Khan, Katrina Kaif, and Anushka Sharma. 123mkv Jab Tak Hai Jaan
So the complete text as a filename would be: 123mkv Jab Tak Hai Jaan 2012 Hindi 720p.mkv (or similar, depending on resolution/quality). The 123mkv part is likely a release group