If you see droppings then there are "kick out"holes which you should be able to find on the wood where the termites that are inside the wood are kicking out their pellets onto the floor. This will help you zero in on the wood that you are treating.
Both Termidor (fipronil for termites) and bora-care will work, but Bora-Care is typically the better one to use for this situation. Termidor is not a wood treatment product, so for it to work you have to drill holes EXACTLY where the termites are and it has to touch the termites to work. If you miss where they are, it will not work. Also, Termidor does not really have any residual in the wood, so after you treat inside the wood with Termidor and it dries, that wood is exposed for future termite and beetle infestations.
Bora-Care is usually the preferred choice if most of the wood is exposed and it is raw wood you are treating, meaning it is not painted, stained, or sealed, it is just normal wood. Bora-Care is made only for wood, and you do not have to know exactly where the termites are for it to work which is a plus. Bora-Care is sprayed evenly over all exposed surfaces of the wood and actually penetrates through the entire piece of wood. When the termites in the wood try to consume the wood after it has been treated, they ingest the Bora-Care with the wood and die. No matter where they are in the wood the Bora-Care will find them as long as you treated the exposed wood that you can see. The other main benefit is that Bora-Care stays in the wood forever, so you will not have to worry about termites or beetles infesting the wood that you treated ever again.