Check out: https://info2.magento.com/rs/magentosoftware/images/Magento_Community_Edition_User_Guide_Latest.pdf
On Page 671, this document provides instructions for exporting your Product data.
You can use these instructions to export your product data, and see what the formatting looks like in CSV format.
You can reference page 665 for information about CSV structure, etc.
You can make adjustments, and then refer to page 668 for instructions on how to Import your edited file.
***I'm not sure if you'll be able to import Tiered Prices through this method without some customization. I recall using Magento Extensions to assist with this in the past, like:
Important note: Magento 1.x has reached end-of-life, so be sure to let the person you're helping out know that they should be patching using something like Mage-One or OpenMage and taking other security precautions while they consider their next move, whether that's to Magento 2 or another platform. Check out https://www.magentoassociation.org/commerce-co-op/full-article/magento-1-post-eol-resources-1 to learn more about resources that can help.
Best of luck!