I would like to know about lists of domain names and their costs or appraisals.
Which sites do you recommend?

Go to Register.com to check the availability of a domain name

Singular .com and .org domain names cost something betwreen $8 - $10
You can go to godaddy.com for them

If you have some domain name ideas and want to register through a bundled product and service site like Gate or others, you can check out the availability of the desired doman name and get it registered at the same time, usually for a decent price. And they will remind you when it expires and renew it for you. Some sites are pretty expensive, so do some shopping before you settle on a bundled service site and be sure they offer services for site traffic statistics, etc.