You can't move apps, you can move little pieces of apps, but since each piece leaves a pointer to itself you don't really save much space. This is assuming that you installed the SD card as portable storage.
If you took the default - adoptable storage - you no longer have an external SD card (logically, even if you have one physically) - the phone has adopted the SD card as part of internal storage, making your internal storage larger, but not allowing you to move anything to the card, since installing apps may install them to the physical eMMC storage in the phone or the SD storage on the card.