How can I make sure I am not infringing copyrights when selling items online?

I have a shop in an eCommerce store, I have a trade license under General Trading here in the UAE that allows me to sell, buy, export... etc. products.

I got an email from the store asking me to sign an attestation regarding all of my products for branded and copyrighted items. I sell Korean products that I buy from the source and sometimes from smaller shops that were able to get the products before me.

Among the products that they gave me as examples were a shirt and pants-inspired outfit from a well-known Korean show. This was handmade by a small business in Korea.

The show did not to my knowledge (even after research) sell such merch. I know that if someone sold a fake item that the brand sold it means they are infringing the copyright, but I am still unsure of the item mentioned above and if what I think is correct.