what if conda has no package?
Activate your conda environment, then use the pip that will also be in your environment (just like the Python interpreter is that of you activated environment).

For example:

source activate your_tf_env          # now we are in the conda env
which -a pip                         # should list all pip executables


The first pip one should be in your_tf_env somewhere.

Now you can simply install your package, e.g. using pip install fastai, which will use the pip of your environment and the package will also be installed in your environment. You do not need to manually copy the files anywhere.

With your conda env still activated, you can then confirm the package is installed by running:

conda list                     # list all installed packages
conda list | grep fastai       # grep filters results, e.g. for  "fastai"