They come alongside the Japanese release.
The three ports are the same games that released on the PlayStation 4 and Nintendo 3DS in Japan on August 10, 2017. The Nintendo Switch release will be the first time they are available outside of Japan.
Dragon Quest, Dragon Quest II: Luminaries of the Legendary Line, and Dragon Quest III: The Seeds of Salvation cost $4.99, $6.49, and $12.49, respectively. Though a physical version of the official Western release has not yet been confirmed, a physical version with English language support can be purchased from Play-Asia.
The most recent game in the main series, Dragon Quest XI S: Echoes of an Elusive Age Definitive Edition, an enhanced Nintendo Switch version of Dragon Quest XI, will also release worldwide on September 27, both physically and digitally. A demo for Dragon Quest XI S is currently available on the Nintendo Switch eShop and save data can be transferred to the full game.