I'm only going to suggest critique groups I've used in the past. But I will warn you upfront, not all critiques will be helpful, some might hurt your feelings and have no basis for what they say, some will be excellent with great suggestions, and I've also received critiques by people who like to read and write, but aren't at the place I'd like them to be as far as writing and critiquing knowledge.
Scribophile is probably my favorite, of the ones I've tried. There are several ways to post your writing. You can also join a critique group, for instance, a picture book or science fiction group. By doing that you are more likely to receive critiques by people who are more familiar with your genre.
Scribophile also runs contests which can be fun, if that's something that appeals to you.
The way to get your story critiqued is to earn karma. You earn karma points by writing critiques for others and also by having them react positively to your critiques. You can earn more karma for critiquing a story in one of the spotlights. And the longer the critique, the more karma you'll receive. Then you spend your earned karma by posting one of your stories. If your story is short, you will probably post the entire thing, otherwise, you might post chapter by chapter so that it won't exceed their suggested limit of words.
Critique Circle is another group I've joined in the past. Like many groups, you earn credits by critiquing other stories. Then with your earned credits, you are able to post your work to be critiqued. Since only a certain number are posted each week, you may have to get in a queue and wait a little while. Again, like most groups, by critiquing stories that come up each week you will earn credits to use in posting your work.
When you join Critique Circle you get some free credits which you can use toward the cost of posting your first story, which will be in the Newbie group. You then have a choice of specifying who can critique you stories, which is a good thing, since as I mentioned earlier some critiquers enjoy reading but aren't going to be too helpful.
Again, it's been a little while since I've posted here, so you might want to see if any of these facts have changed.
Society of Children's Writers & Illustrators is another great group to join. While this is not a free group, they offer lots of avenues for the writer or illustrator of children's literature. Whether you are interested in meeting critiquers in person or online, you should be able to find a group.
SCBWI is a wonderful place to find an exchange of knowledge between writers, illustrators, editors, publishers, agents, librarians, educators, booksellers and others involved with literature for young people. There are currently more than 22,000 members worldwide.
Check out their site: SCBWI.
I'm sure there are many more critique groups, but I only feel comfortable posting about the ones I've been involved with. I hope if a group is what you're looking for, that this information has been helpful.