The CJL3400E breaker is obsolete.
The Replacement breaker is a Square D LHL36400 breaker with a LACMH mounting kit. These breakers are rated 25KAIC at 600V.
You can also use a LAL36400 with the LACMH which has a rating of 22KAIC if the required KAIC in the panel is 22KAIC or lower.
The LACMH is a single breaker mounting kit. The CJL breaker could be double mounted, one mounted on each side of panel. Double mounting is no longer available with the LACMH.