The following are the expansions for Tom Nook's store and how to obtain them:

Nook's Cranny: Available at start.

Nook 'n Go: Buy 25,000 Bells worth of merchandise.

Nookway: Buy 65,000 Bells worth of merchandise.

Nookingtons: Buy 240,000 Bells worth of merchandise and have a visiting friend buy something from Tom Nook. Note: This version of the store includes a hair salon.