how to go about saving items in a players inventory?

i don't know how to even go about saving items a player has bought in the store.. can i be helped

You'd want to look for DataStoreService here.

What you could do is save all the names of the items in the inventory in a table with a unique key. When the player joins the game, you can go through all names in the table, find them in a folder of items, and parent it to the player's inventory folder - if it exists.