How do you upgrade tom nooks store in animal crossing wild world?

Answer 1

The upgrades to Tom Nook's store are as follows:

• Nook's Cranny upgrades to Nook 'n' Go after a total of 25,000 bells has been spent there.
• Nook 'n' Go upgrades to Nookway after a total of 90,000 bells has been spent there.
• Nookway upgrades to Nookingtons after a total of 240,000 bells has been spent there, and a player from another town has bought at least one item there.

Upgrades will be announced on the bulletin board a few days in advance, and the shop will be closed for remodeling for a day.
you pay your loan

Answer 2

You have to spend a certain amount of bells to upgrade the store(s). Usually about 20,000 bells to 500,000 bells. But you don't have to spend the bells all at once. You can spend as much as you want and buy stuff as long as all the bells you spent all add up to that certain amount or more. Hope this helped! :)