When macOS tries to run an app that is not built for Apple silicon, macOS will prompt to install Rosetta 2 to automatically translate the app to Apple silicon.
In Terminal, there is no automatic detection for missing Rosetta to run older architecture command line tools.
If you haven't been prompted for any other app already, manually install Rosetta 2:
If you need to run a universal binary in the previous architecture, use
arch and specify the architecture. You need to manually specify the architecture for binaries that need to run other binaries that are not built for Apple silicon, like Homebrew.
arch -x86_64 …
arch -x86_64 brew install packagename
Alternatively, you can run the entire Terminal app using Rosetta by opening Get Info on Terminal.app in Finder and checking ‘Open using Rosetta’. This way will Terminal and every binary it tries to run through Rosetta, so Apple silicon binaries won't be supported and performance will be impacted, but you don't need to specify the architecture to run old binaries.
To switch an existing zsh terminal to x86_64 use this command:
arch -x86_64 zsh