> Currently i have pd4ml.volume.371b9 version which supports PDF/A.

It is not quite correct. You own the regular volume license. There is also “PD4ML Volume DMS Edition”, which adds PDF/A support. (Its distribution includes pd4ml_rc.jar).

> PDF/A generated using Pd4ml jar is of which conformance level?

For the time being it is PDF/A-1b. We plan to implement tagged PDF output for PDF/A-1a conformance.