Please don't worry. The snails won't harm your fish.
Where are your snails? Well, they might be hiding someplace while they get used to the new tank. Or the fish may have bothered or nipped at them so they are hiding. Sometimes snails can go into or, if they are small enough, get sucked into the inlet side of the filter. They can also hide behind the filter or in the top inside of the filter. If you have a tank cover, hood, or light fixture, then they may be up there. They can also hide behind the heater. They may be inside or on the inside 'ceiling' of any decor or hiding spots you have.. Some snails may 'escape' and leave the aquarium if they are unhappy with their living conditions for some reason, for example, bad water quality, or dirty water, or not enough food that they want to eat. It's also possible the fish ate them, depending on the size of the snails and the size and type of your fish.
However, they are probably just someplace where you can't see them and I think If you keep looking you will eventually see them.