We are inspected by the State of CA 2x a month for pests and these gnats are harmless! We rarely see them in our greenhouses, but occasionally they will hitchhike and appear upon opening a box.
The quickest solution is to spread the succulents out on a table, cookie trays etc. and allow them to completely dry. Be careful of direct hot sun as they can be sunburned - a shaded patio, porch etc. is best.
Also place them somewhere that they can get a good flow of air over them, even using a house fan to blow over will help. You can also check each one as usually it’s just 1 or a few types that may have them. If they don’t have any, move them completely away from those that do.
After the soil has dried completely, they should all be gone. Some dish soap mixed with some water can be used to water the plants on their first watering.