@Solaris yes, you can activate the old environment if you have created on Anaconda while using the below command.
[base] path: conda activate [your environment name]
You need to go to the project folder and just train bot and run rasa shell --debug
Note: Above command will be used for Window only. Note: If you forgot the environment created check the environment folder in Anaconda under env
Or if you need to create a new environment, you need to install rasa or if you need to install rasa x you can follow these steps from my suggested thread :