You're welcome! (for "thank you") = ¡De Nada!

You say "de nada"

por nada

Do you mean "your welcome" or "you're welcome"? your welcome = "tu bienvenida" (or "su bienvenida"); or using the second person plural "vuestra bienvenida" you're welcome = "de nada"

you're welcome = para nosotros es una manera de agradecer y significa "de nada" or "gracias"