will in get admission in dtu with jee rank 31900 and def quota priority 6 . outside delhi

Since defence quota has a huge priority in JAC counseling so you hold a very strong chance of finding a seat in DT or NSIT

With this rank and quota you can have a chance of getting ME or EE branch

I would like to add, I would recommend you to prefer NSIT over DTU. This I've given from the opinions of best of colleagues well performing in both the colleges.

Hope it helps