Please recommend or provide information about sunscreen (I have never applied it in my life).

I'm worried about aging because I didn't apply sunscreen in my question post. Where should I go for skin care in this case?

I gave it to you, but there are no comments..

Since I've never used it before, I don't know the figures, and there are so many products to choose from that I really don't know which ones are good.

Please recommend any good products you have personally used.

Additionally, there are some indices and numbers mentioned, and I am curious about what these are.

As someone who has never paid attention to skincare or even tried a mask (for your information, I am a man), I feel a bit embarrassed to ask such a basic question, but I am a little worried.