what kind of tax we need to pay if I re-sell products

If the resale of these products is considered by the IRS to be a business (see When the IRS Classifies Your Business as a Hobby), then self-employment and income taxes may be due on the net income of this business.  

• Self-employment taxes are calculated at 15.3% of the net profit, and
• Income taxes are calculated on your total income including the net profit from this business.

This article will provide some additional detail:  A Freelancer's Guide to Taxes 

Also, you will need to track all of your product cost expenses whether you make the products yourself from raw materials (vendor receipts), buy the product to resell (also from vendor receipts), or receive the product as a gift (what the donor spent to purchase the product).