I want to know which is the best free theme to design a e-commerce website with more than 100 products
That’s quite ambiguous - for example on Wordpress? Prestashop? Magento? Shoplift? Etc.
That’s quite a lot of products for a free option and you are almost certainly going to find features being very constrained
I am so sorry for not to be specific. But I really want to know which platform is best for creating an e-commerce website.
It depends on so many things like how technical your knowledge is? What products you are selling? What payment systems are needed? Who/how would handle that? Etc etc
Every platform has its advantages and disadvantages.
Speed can be an issue with a lot of products if they each have a lot of variations.
In addition, do yourself a favour and buy a theme! It will pay itself back in no time.