Magento – Export all categories & products then import them

To associate products with categories in Dataflow you'll need two pieces of data:

• Sku (Configurable, Simple, doesn't matter)
• The target Category IDs

The field for the category IDs needs to be comma-separated itself, so make sure it's quoted if you're manually creating it:

sku,category_ids
ABCD1234,"1,2,3,4,5"
L0S7,"4,8,15,16,23,42"

Save it to disk as a .csv file, and you can upload it to the All Products Import default dataflow profile. This will replace all current categories for the skus listed, so take caution and make sure to get a list of pre-existing category associations.

If I understand correctly you are using Magento DataFlow export which is quite outdated.

I suggest using Magento's ImportExport (System\ImportExport\Export). It exports all gallery images into a _media_image column.