Here are some web pages with ideas about how to store and display your collections:
The Science Museum Museum has some advice on home nature museums: Make your own museum | Science Museum of Minnesota (smm.org)
Build a Homemade Natural History Museum:
https://childhoodbynature.com/build-a-homemade-natural-history-museum/
Ideas for Displaying Rocks and Fossils:
https://earlylearningideas.com/geology-lab-dramatic-play
https://detectingdaily.com/rock-collection-display-ideas/
Ideas for Displaying Shells:
https://www.completely-coastal.com/2013/02/seashell-collection.html