If you are using any version prior to 2.0.2, you first need to upgrade to 2.0.2. You can do that by downloading it from http://www.j2store.org/downloads.html
1. BACKUP! BACKUP! BACKUP! - Use Akeeba Backup to backup your entire site.
2. Download J2Store 2.5/2.6 from http://www.j2store.org/downloads.html (PRO subscribers from My Accounts->My Downloads area.)
3. Go to Extensions Manager and Install.
4. Go to Components->J2Store. The Dashboard shows you some important information about migrating things. Read them carefully and follow the instructions given below.
1. Tax Profiles
On J2Store 2.5, we have introduced a better tax system which is based on Geozones. In previous versions, you can just create and apply one or few tax profiles across the store.
Now, you have more control over the tax configuration. You create tax profiles that automatically apply rates based on the billing, shipping or store addresses.
So you have to create tax profiles once again based on the new structure. This is very IMPORTANT step.
To know about how to set up the Geozones, tax rates and tax profiles correctly, please watch the video tutorial below.
a. Create a store profile (you will be selecting the default country and zone/region/state for tax calculation)
b. Create Geozones and add countries and zones to them.
c. Create tax rates for each Geozone
d. Create tax profile and map the tax rates to an address type. (You can apply one tax based on billing address and another on shipping address).
2. Product Attributes Migration
J2Store 2.5 also implements a new, improved structure for product attributes/options. So you have to migrate your old attributes.
We have included a tool for automatic migration. All you have to do is
a. Go to J2Store->Tools->Migrate Attributes.
b. Click start migration.
In case, you have used = as the price prefix while creating attribute options for some of the products, you would see them listed in the screen.
If you see any products listed, the migration tool won't convert the attributes associated with those products. You have to manually migrate them.
Watch the video below for a better explanation