Appraisals for insurance purposes aren't cheap. I assume you know what you bought- ie akoya or Tahitians etc. and how much you paid for them.
It will be hard to find who is really competent in pearls. However, you should call the major jewelers and ask if they have a pearls specialist and/or how much they know about pearls- ie anyone ever take the GIA pearls course or if they know of someone who really knows pearls.
Note. There is huge disconnect between most appraisals and what the pearls will actually bring on the market except in a retail B&M store, where you pay top $$ and will never see that price realized again.
We would really love it if you put up a few pictures, here. We may be able to tell you something about the pearls.