Can I say 1PCS when the quantity is one?

It’s said in a dictionary that PCS is the abbreviation of Pieces. So 20 PCS means 20 pieces of something.

My question is ,when the quantity is one, should I say 1 PCS, or 1 PC, or something else?

Thanks in advance! 🙂

Here is a dictionary link.

http://www.abbreviations.com/PCS