Migrating from Old domian to new Domain and 301 Redirect

Hi All,

We are in process of migrating from our old domain to new domain and everything has been set except one thing which i am not sure how best can be handled.
The old domain is running from last few years and have quite good in search hits and indexing and we want to preserve as much as possible when it comes to SEO and search engine visibility.

Since Database is same so this means if the article in the old domain is at
https://www.olddomain.com/category/my-article it will be at this location in new domain
https://www.newdomain.com/category/my-article
i know about that we can set 301 redirect in the .htacces file but not sure how to do this

1. Do i need to have mapping of each individual old URL to its equivalent new URL
or only a single 301 redirect will be ok.Is there any other way to achieve this in the word-press.

any help in this regard will be helpful