I tried to research online but didn't really find an answer. I am totally new in coding and it'll be really helpful if you can make the answer in detail.
Could you add an attribute to your products for 'Amazon URL' and then add this to your product page template?
In your back-end navigate catalog/attributes/manage attributes then create the attribute, and then add it to your products' attribute sets in catalog/attributes/attributesets
from there, create a copy of catalog/product/view.phtml in your theme design folder which includes the following button:
<a class="button" href="<?php echo $this->getProduct()->getAmazonUrl(); ?>"> Buy from Amazon</a>
This will add that link to your product page, and you could place it wherever you wanted.