Assuming I have an Amazon product URL like so
http://www.amazon.com/Kindle-Wireless-Reading-Display-Generation/dp/B0015T963C/ref=amb_link_86123711_2?pf_rd_m=ATVP
Try using this regex:
(?:[/dp/]|$)([A-Z0-9]{10})
Check out the demo: https://regexr.com/3gk2s