find . -type f | wc -l will recursively list all the files (-type f restricts to only files) in the current directory (replace . with your path). The output of this is piped into wc -l which will count the number of lines.

Refs:

• https://stackoverflow.com/questions/9769434/how-to-count-all-files-inside-a-folder-its-subfolder-and-all-the-count-should/9769492