sharepoint online – Can’t get the file extension in Flow

I can’t get the file extension after Flow sends me an email. I searched through the web and saw that I can use metadata, but after I added metadata, there’s a condition but the expression for the condition won’t work at all.

@not(empty(body('Get_file_content'))) 

I saw they used to have the advanced function but it’s not available anymore. I cant add it in the expression either, as it’s invalid.

Is there another way I can get the file extension in my email attachment?

Thanks in advance.