Can all items that are in the market place and not made by Epic be used in a paid game?
Of course, as long as you bought them you can do pretty much anything except resell them.
Heres a simple FAQ, search for the EULA for more details.
https://www.unrealengine.com/marketplace/marketplace-business-terms-faq
Don’t forget to accept an answer that best clears your question up or answers it so when the community finds your question in the future via search/google they know exactly what you did to fix it/get it going as well as keeping AnswerHub clean so that it gets removed from the “unanswered questions” category.