C'après-midi

 It appears that you've written "C'après-midi." However, the correct spelling is "Cet après-midi" or "ce après-midi."

In French, when you're referring to "this afternoon," you use "ce" or "cet" depending on the gender of the noun that follows. 

Since "après-midi" is masculine, you would use "ce" if the next word begins with a consonant and "cet" if it begins with a vowel.

Examples:

"Ce après-midi, je vais au cinéma." (This afternoon, I am going to the cinema.)

"Cet après-midi, il fera beau." (This afternoon, the weather will be nice.)

Remember, "ce" is used before masculine words starting with a consonant, and "cet" is used before masculine words starting with a vowel or silent "h".