In this level the password is stored in the file data.txt, which contains base64 encoded data.
When we view the contents of the file we are greeted with this:
Because this data is encoded as base64, we need to decode it. This can be done with base64. To decode data the flag -d is used
base64 -d data.txt
This reveals the password: 6zPeziLdR2RKNdNYFNb6nVCKzphlXHBM