Need help on creating reminder in the item card in the inventory section. This reminder should remind that the item in stock has reached to a minimum of like say 10. so that a new stock can be bought.

why dont you use Planning Worksheet, use Calculate Regenerative Plan. or use Requisition Worksheet.

The reorder policies and replenishment settings do this for you, alternatively you can not run planning and run the inventory report on critical stock or stock levels, cannot remember its name, but this relies on you running it and has no integrated planning functions.

Essentially as Joe says, use the planning tools.