Can I tenderize conch meat with baking soda
While you might get a tiny bit of tenderizing from a baking soda soak, it won't do much to transform the physical structures that make conch tough.  Mechanical tenderizing is the way to go - together with (typically) a very long and slow cooking time, or possibly cooking with a pressure cooker.

If you decide you want to try a baking soda "brine" I would recommend soaking briefly AFTER you pound the conch and making sure to wash the conch thoroughly afterwards to make sure you don't retain a soapy taste of baking soda that would ruin the subtle flavor of conch.

If you are interested in a chemical tenderizer for conch, you might consider some form of acid-based marinade - although, again, a marinade is going to transform the delicate flavors that characterize conch.

Basically, if you want to enjoy the conch-y taste of conch, I would go for tenderizing with a mallet and judicious cooking only.  

See also:  How should baking soda be used to tenderize meat?