Hi Kanwaldeep,
" in case of porting Eb3- EB2, how long did it take from I140 approval to getting 485 approval"? No exact answer. check the below thread:
http://www.trackitt.com/usa-discussion-forums/i485-eb/853756759/gc-approvals-on-eb3-to-eb2-porting-applicants/page/last_page
My I-485 is approved after 2.5 months of I-140 approval.
In my case, I don't know what my attorney sent with I-140. I got old PD with new I-140. I sent interfile emails to NSC & TSC, as my I-140 approved at NSC and I-485 is at TSC. I also sent a snail mail interfile letter to TSC (doesn't hurt).
Best of luck in your I-140 & I-485, hope they will be approved soon.