Open terminal and go to your project's lib folder. After that run the command below.
Flutter
find . -name '*.dart' ! -name '*.g.dart' ! -name '*.freezed.dart' ! -name '*.gr.dart' ! -name '*.gen.dart' | xargs wc -l | sort -n
For Any Langauge find . -name '*.FILE_EXT' | xargs wc -l | sort -n
FILE_EXT
can be .kt
.dart
.java
etc
Without excluding any file
find . -name '*.dart' | xargs wc -l | sort -n