If you want to keep python 3, you can follow these directions to create a python 2.7 environment, called py27.
Then you just need to activate py27:
$ conda activate py27
Then you can install spyder on this environment, e.g.:
$ conda install spyder
Then you can start spyder from the command line or navigate to 2.7 version of spyder.exe below the envs directory (e.g. C:\ProgramData\Anaconda3\envs\py27\Scripts)