Where can i find templets which contains register and login pages
Of course they do
Let’s pick one at random. Let’s take the latest theme there: http://themeforest.net/item/atlantic-news-responsive-wordpress-magazine-blog/2905407
Click on ‘Live Preview’, then click on ‘Remove frame’ on the top left. You are now at this address: http://wp.color-theme.com/atlantic/
Add ‘wp-admin’ after it: http://wp.color-theme.com/atlantic/wp-admin
And there we go, a login screen. If the author had enabled registration, you’d see a Register link as well.
Additionally, if you need that login/registration form to be inserted in your site, there are WordPress plugins that do that