What you are looking for is a board to board connector, check a distributor like mouser or digikey for the pitch and spacing height you want. You can also get 0.1" headers that are male on both ends so you could just solder the boards together if you don't want a connector.
Another way to do this is with 0.1" headers that are very long and have both male and female ends to stack PCB's, simmilar to arudino hats.