Yes you can put transmission fluid in your transfer case.
Most transfer cases for automatic transmissions can use the same automatic transmission fluid as the automatic transmission.
Whenever you check your transmission fluid you should also check the transfer case fluid because the transfer case is operating all the time whether or not you're using the 4 wheel drive.
The gears are spinning in the transfer case all the time.
So if the transfer case runs dry it will be destroyed and cause an expensive repair bill.
Transfer cases can also be filled with gear oil as well.