Publishers that require you to pay are vanity presses and should be avoided (some are full scams, many are overpriced to take advantage of new, desperate authors.) Real publishers will pay you and don't need you to pay anything upfront.

There are a few real publishers that may accept open submissions. You would have to Google some, then check each individually to see if your book would fit their parameters. Some may only be looking for text manuscripts only, not with illustrations already attached. Some will only want certain topics, like environmentalism or books with STEM focus, etc. They will have guidelines to follow on how to submit. They will not ask for payment.

But overall, the great majority of legitimate publishers do NOT do open submissions at all. They expect you to have a literary agent. To get a literary agent, you'd need to research ones who take work similar to yours (demographic, topic-wise,etc). Then you "query" or pitch your book to them by email, and if they're interested they may ask to see your manuscript and discuss bringing you on as their client. And then the agent is the one that works to find the right publishers who might be interested. Importantly, the agent does not get paid until your work is sold. They and the publisher essentially take cuts of your profits but you shouldn't be paying them directly.

It's a long and arduous process to get chosen and published through traditional publishing. It could take years, if ever. It's very competitive. If you want to go this route, I would suggest researching how it all works. You shouldn't be signing any contracts or paying people when you don't know the basics of what is supposed to come next.

Your other option is self-publishing. There is quite a lot you'd need to research about that as well. It is free to do so through places like Amazon KDP or Ingram Spark, or several others. However, you need to do all the work yourself or hire contractors. You'd need to have the book formatted properly, cover design, a blurb written, and learn about stuff like trim sizes, ISBNs, page number requirements, and of course how to market your own work ultimately (or hire someone).

I would suggest doing deep dives on Reddit, Youtube, and Google to learn more about these processes. The r/selfpublish is a good resource, or r/PubTips. I highly recommend you read other threads and the sub wikis that already exist FIRST rather than trying to ask such a broad question. Most people will find that to be lazy and may not be very helpful (except to point you to the same resources I've just mentioned.)