Can't make a 301 redirect, or am I doing something wrong?

Question

opencart

I can't do a 301 redirect, or I'm doing something wrong.
Version 2.1. Opencart
What exactly needs to be written so that from the page
2031.technol.com/namecatalog/nametowar
it gets to
2031.technol.com/nametowar
The fact is that the same product is obtained under different links, and this is a duplicate content. This, as I understand it, is critical for website promotion ..
How to make a product open on one link?