The error you're seeing means that the Dart SDK version you're currently using (2.10.0)

is not compatible with the version of the path package you're trying to use (1.8.0

nullsafety.3).This version of the path package requires a Dart SDK version between 2.12.0

and below 3.0.0.

To fix this issue, you have two options:

Upgrade your Dart SDK to version 2.12.0 or higher (but less than 3.0.0),

OR

Downgrade the path package to a version that is compatible with Dart SDK 2.10.0

Happy Coding