Power up the Anaconda prompt with Administrator privileges.
Activate the environment you need to install the package.
activate <your environment name>
then check in the anaconda repo that package is available or not
https://anaconda.org/anaconda/repo
most of the cases you can find the package and on that page, it will mention what is the command that you need to use to install.
conda install --channel "anaconda" package
cheers enjoy ;)
