You should use CSV file (comma separated values).
Each file has rows with such format
Id,Sku,Gtin,ManufacturerPartNumber,Price,ProductCost,OldPrice,TierPricePairs
Id – The product identifier (from the current store). Required. Larger then 0.
Note. Different stores can have different product ids. 0 is wrong value.
Sku - Product stock keeping unit (SKU). Can be empty.
Gtin - GTIN (global trade item number). Can be empty.
ManufacturerPartNumber - Manufacturer part number. Can be empty.
Price - The price of the product. Required. Example. 1245.12, 0.99, “1234,99”, “0,99”.
ProductCost - Product cost. Required. Example. 1245.12, 0.99, “1234,99”, “0,99”.
OldPrice - Old price. Required. Example. 1245.12, 0.99, “1234,99”, “0,99”.
(removed from nop 3.90) SpecialPrice - Special price. Can be empty. Example. 1245.12, 0.99, “1234,99”, “0,99”.
TierPricePairs (full format for nop 3.90 and never) – Tier Price Pairs. Can be empty. It has the next format
{Quantity:Price:CustomerRoleId;Quantity:Price:CustomerRoleId; ... }
{Quantity:Price:CustomerRoleId:StoreId;Quantity:Price:CustomerRoleId:StoreId; ... }
{Quantity:Price:CustomerRoleId:StoreId:StartDate;Quantity:Price:CustomerRoleId:StoreId:StartDate; ... }
{Quantity:Price:CustomerRoleId:StoreId:StartDate:EndDate;Quantity:Price:CustomerRoleId:StoreId:StartDate:EndDate; ... }
Note. String begins from {, and ends }. Each pair has the next format Quantity:Price.
Quantity – Numeric. Example. 1, 2, 36.
Price – Example. 1245.12, 0.99, “1234,99”, “0,99”.
CustomerRoleId – Example. 0, 1, 2, (0 - for all customer roles)
StoreId – Example. Example. 0, 1, 2.
StartDate – Example. format dd/MM/yyyy
EndDate – Example. format dd/MM/yyyy
