power automate – I cant get the file extension in flow

I cant get the file extension after flow send me an email. I search through the web and I saw that I can use metadata but after I added metadata, there will be a condition but the expression for condition cant work at all.

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

I saw that previously they used to have the advanced function but now this is not available anymore. I cant add this in expression too as its invalid.

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

Thanks in advanced.