Souffle's advice is good
I'd second just having one hamster in the Eco Habitat. If you did have a litter of 6 or so, then once they are weaned, if you can't find buyers then maybe you could give them to the pet shop to sell for you.
Yes it's outrageous they make these mistakes with sexing and sell pregnant hamsters even - it happens a lot. Pet shops aren't always that knowledgeable about hamsters!
What most people do is advertise locally - eg a in a shop window - or a local Facebook website for the area eg. Or on Gumtree etc in the Uk. You;d be surprised how many people want a pet hamster - that's why your pet shop has them
And then leave giving them to the pet shop as a last resort. If she has the babies, then start advertising and making a shortlist of people who are interested and keep them updated.
As Souffle says, the baby boys could go in a cagewith the Dad and the girls with the Mum, until homes were found.