Optimization of the form for issuing news, will it hurt or help the site?

Question

Apache HTTP Server

Now the site has about 300 news articles collected over several years of the site's operation.
News is displayed as www.mysite.com/news.php?id=299
I want to do it the smart way: www.mysite.com/news/my-mega-novost.htm
Technically I know how to do it, that's not the question.
I would like to know the following:
1) Will such castling damage the site from the point of view of search engines? As far as I understand, now all my 300 articles are indexed as ?id=xxx.
2) Both methods of calling the article will work for me. It turns out duplication of content, which is also bad in theory ...
How to act competently in this situation? I read about some kind of error 303, but did not understand anything.

Answer 1

Make a 301 on the old URLs - Moved permanently: www.checkupdown.com/status/E301.html
This will tell search engines that this page should be searched on the new URL that you will give along with the 301 status.

Answer 2

301 redirect as already written above and plus prohibit indexing by old urls in robots.txt. Perhaps a couple of updates will be some decline on these pages, and then everything will work out.

Answer 3

Everything works, thanks guys

Answer 4

can be put in meta and rel="canonical"

Answer 5

I did it like this (news.php file):
- If the id comes, then the old link worked. Request to the database, take out my-mega-novost, then
Header( "HTTP/1.1 301 Moved Permanently" );
Header("Location: www.mysite.com/news/my-mega-novost.thml ");
- If my-mega-novost arrives, we simply display the news.
Yandex instantly re-indexed the site, I did not notice any decline at all. True, and there is not much sense yet. Apparently we have to wait a bit.