If you want to make your rifle into an "Enemy at the Gates" WWII model you can buy the scope and put it on. The later day made Russian copy production scopes with mounts will do the trick and be just like the originals.....except an expert gunsmith won't have put it on and made it "sniper" standard and they cost about as much as the rifle they are put on....or more. If you just want to shoot with a scope I'd get what we call a "scout mount". It goes on where the regular rear sight goes. It has the benefit of not needing to modify your straight bolt handle and at the same time you can remove the steel sight and put on the mount without having to drill any holes in your barrel. And.... you can put the rifle back to it's original condition later by replacing the original iron site if you want to remove the mount. These things can be any price from $10 and going up.
The best and most in demand in the US, among milsurp fans, is one made by Darrell. Darrell lives about 6o miles from me and I've seen his mounts and met him. His mounts are serious and rock solid and are mounted on the rear Nagant sight. His mounts are on the pricey end, but worth it for some serious shooters. But.. he seems to have gotten out of the notion of making them.
Here's a video ...among several... that will show you what the scout mount idea is about and how to put one on. This one is on the cheap side and Darrell didn't make it.
https://www.youtube.com/watch?v=WkLcfxNNNjc
I'll attach an image of my Russian sniper......more or less correct. The one I have wasn't war used as a sniper, I don't think, but some kind of after war construct with period correct scope and war era otherwise correct 91/30.
My experience with the Russian war design scope is that the magnification isn't much better than iron sights and the scope itself has a tendency to get out of adjustment from vibration quickly. But.... Dutch Mosin and others may have had more positive experiences. Maybe I need to tighten the screws and add some locktight.