Can Not Copy from PC to Nas

I am having issues trying to copy files from PC to NAS. I can access the NAS and all of it’s directory’s.
I can copy files from nas to pc. But when i select files from PC and copy to NAS. I use explore select files go to destination on nas and when i select paste…the paste function is not there…help. I need to copy a bunch of files from my pc to nas.

You probably mapped it using a user ID that has no write access.