How Could I Make A Item Storage Backpack?

Hello. I am a very new scripter and I don’t understand some topics so if you could explain briefly how some of the concepts work/mean. I’m working in a game dev studio and was making a survival/RPG type game.

We have leader stats saving but I would like item saving. I don’t want all items to be saved but rather ones that people put in a backpack GUI and for this GUI to have a max item limit. I’m not sure how I would do this thus I am here for some help.

Thanks- GlitxchSZ

Here is a tutorial you can follow to teach you how to save players items to their backpack: