Where can I find the stock valuation of a listed company?

To have excellent 'raw data': Finviz, it's free mostly

(but I doubt, that these will be of any help in retail investing)​​​

You can look into using Capital IQ, which is a platform that even professionals use in their valuations, as it provides accurate and a large database of past stock information! There are also excel add-ins and various analysis tools that will allow you to deep dive into pretty much any industry. However, you will need to pay for this, unless your educational institution already provides students with free subscription!

If you do not intend to deep-dive, then various online free platforms like Yahoo Finance is pretty good. If you want stock valuation reports, you can also check out reports on various companies done by bank analysts. For a fact, I know DBS has this.

All the best!